HAZARDOUS CHEMICAL SUBSTANCES REGULATIONS

Contents

1 Definitions
2 Scope of application
3 Information and training
4 Duties of persons who may be exposed to hazardous chemical substances
5 Assessment of potential exposure
6 Air monitoring
7 Medical surveillance
8 Respirator zone
9 Records
10 Control of exposure to HCS
11 Personal protective equipment and facilities
12 Maintenance of control measures
13 Prohibitions
14 Labelling, packaging, transportation and storage
15 Disposal of hazardous chemical substances
16 Offences and penalties

Annexure 1 - HCS Guidelines

Table 1
Table 2
Table 3

Annexure 2 - Calculation of exposure with regard to the specified reference periods
Annexure 3 - Methods of measurement and calculation for determining the fibre concentrations of manmade mineral fibre Annexure 4 - Cotton dust
Annexure 5 - Asphyxiants
Annexure 6 - Rubber fume and rubber process dust
Annexure 7 - The definition of grain dust

HAZARDOUS CHEMICAL SUBSTANCES REGULATIONS

[These regulations were first published in GN R1179 of 25 August 1995.]

The Minister of Labour has under section 43 of the Occupational Health and Safety Act, 1993 (Act No. 85 of 1993), after consultation with the Advisory Council for Occupational Health and Safety, made the regulations in the Schedule.

Schedule
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Definitions

1.  In this Schedule a word or expression to which a meaning has been assigned in the Act shall bear the meaning so assigned to it and unless the context otherwise indicates-

"air monitoring" means the monitoring of the concentrations of airborne hazardous chemical substances;

"Asbestos Regulations" means the Asbestos Regulations published by Government Notice No. R. 773 of 10 April 1987 under section 43 (5) of the Act;

"assessment" means a programme to determine any risk from exposure to a hazardous chemical substance associated with any hazard thereof at the workplace in order to identify the steps needed to be taken to remove, reduce or control such hazard;

"BEI" or "biological exposure index" is a reference value intended as a guideline for the evaluation of potential health hazards as listed in Table 3 of Annexure 1 hereby as revised from time to time and listed in the Government Gazette;

"engineering control measures" means control measures that remove or reduce the exposure of persons at the workplace by means of engineering methods;

"exposed" means exposed to a hazardous chemical substance whilst at the workplace and "exposure" has a corresponding meaning;

"EH 42" means the Guidance Note EH 42 of the Health and Safety Executive of the United Kingdom: Monitoring Strategies for Toxic Substances 1989 HSE ISBN 0 11885412 7 as revised from time to time and published in the Government Gazette;

"Facilities Regulations" means the Facilities Regulations published by Government Notice No. R. 2362 of 5 October 1990 under section 43 (5) of the Act;

"General Administrative Regulations" means the General Administrative Regulations published by Government Notice No. R. 2206 of 5 October 1984 under section 43 (5) of the Act;

"HCS" or "hazardous chemical substance" means any toxic, harmful, corrosive, irritant or asphyxiant substance, or a mixture of such substances for which-

(a) an occupational exposure limit is prescribed; or

(b) an occupational exposure limit is not prescribed, but which creates a hazard to health;

"intake" includes inhalation, ingestion or absorption through the skin or mucous membranes;

"Lead Regulations" means the Lead Regulations published by Government Notice No. R. 586 of 22 March 1991 under section 43 (5) of the Act;

"measurement programme" means a programme according to the monitoring strategy as contemplated in EH 42;

"monitoring" means the planning, carrying out and recording of the results of a measurement programme;

"OEL" or "occupational exposure limit" means a limit value set by the Minister for a stress factor in the workplace as revised from time to time by notice in the Government Gazette;

"OEL-CL" or "occupational exposure limit - control limit" means the occupational exposure limit for a hazardous chemical substance as listed in Table 1 of Annexure 1 hereby and "control limit" has a corresponding meaning;

"OEL-RL" or "occupational exposure limit - recommended limit" means the occupational exposure limit for a hazardous chemical substance as listed in Table 2 of Annexure 1 hereby and "recommended limit" has a corresponding meaning;

"OESSM" means the Occupational Exposure Sampling Strategy Manual, published by the National Institute for Occupational Safety and Health (NIOSH), Publication No. 77­173 of 1977, United States of America: Department of Health, Education and Welfare;

"regional director" means the regional director as defined in regulation 1 of the General Administrative Regulations;

"respiratory protective equipment" means a device which is worn over at least the mouth and nose to prevent the inhalation of airborne hazardous chemical substances and which is of a type, or conforms to a standard approved by the Minister;

"respirator zone" means an area where the concentration of an airborne hazardous chemical substance exceeds the recommended limit for that substance;

"SABS 072" the Code of Practice for the Safe Handling of Pesticides, SABS 072, published by the South African Bureau of Standards (SABS);

"SABS 0228" the Code of Practice for the Identification and Classification of Dangerous Substances and Goods, SABS 0228, published by the South African Bureau of Standards (SABS);

"SABS 0229" the Code of Practice for Packaging of Dangerous Goods for Road and Rail Transportation in South Africa, SABS 0229, published by the South African Bureau of Standards (SABS);

Scope of application

2.  (1)  Subject to the provisions of subregulation (2), these regulations shall apply to an employer or a self-employed person who carries out work at a workplace which may expose any person to the intake of an HCS at that workplace.

    (2)  The provisions of regulations 3 (1), 6 and 7 shall not apply to-

(a) a self­employed person; or

(b) a person who visits a workplace as contemplated in subregulation (1).

    (3)  The provisions of these regulations shall not apply in the case where the Lead Regulations or Asbestos Regulations apply.

Information and training

3.  (1)  An employer shall, before any employee is exposed or may be exposed, after consultation with the health and safety committee established for that section of the workplace, ensure that the employee is adequately and comprehensively informed and trained, as well as thereafter informed and trained at intervals as may be recommended by that health and safety committee, with regard to-

(a) the contents and scope of these regulations;

(b) the potential source of exposure;

(c) the potential risks to health caused by exposure;

(d) the potential detrimental effect of exposure on his or her reproductive ability;

(e) the measures to be taken by the employers to protect an employee against any risk from exposure;

(f) the precautions to be taken by an employee to protect himself or herself against the health risks associated with the exposure, including the wearing and use of protective clothing and respiratory protective equipment;

(g) the necessity, correct use, maintenance and potential of safety equipment, facilities and engineering control measures provided;

(h) the necessity of personal air sampling and medical surveillance;

(i) the importance of good housekeeping at the workplace and personal hygiene;

(j) the safe working procedures regarding the use, handling, storage and labelling of the HCS at the workplace; and

(k) procedures to be followed in the event of spillages, leakages or any similar emergency situation which could take place by accident;

    (2)  An employer or a self-employed person shall give written instructions of the procedures contemplated in paragraph (k) of subregulation (1) to the drivers of vehicles carrying the HCS.

    (3)  An employer or a self­employed person shall ensure that he himself or she herself or any person who in any manner assists him or her in the carrying out or the conducting of his or her business, have the necessary information and has undergone sufficient training in order for him or her to identify the potential risks and the precautions which should be taken.

Duties of persons who may be exposed to hazardous chemical substances

4.  A person who is or may be exposed, shall obey a lawful instruction given by or on behalf of the employer or a self­employed person, regarding-

(a) the prevention of an HCS from being released;

(b) the wearing of personal protective equipment;

(c) the wearing of monitoring equipment to measure personal exposure;

(d) the reporting for health evaluations and biological tests as required by these regulations;

(e) the cleaning up and disposal of materials containing HCS;

(f) housekeeping at the workplace, personal hygiene and environmental and health practices; and

(g) information and training as contemplated in regulation 3.

Assessment of potential exposure

5.  (1)  An employer or self­employed person shall after consultation with the relevant health and safety representative or relevant health and safety committee, cause an immediate assessment to be made and thereafter at intervals not exceeding two years, to determine if any employee may be exposed by any route of intake.

    (2)  An employer shall inform the relevant health and safety representative or relevant health and safety committee in writing of the arrangements made for the assessment contemplated in subregulation (1), give them reasonable time to comment thereon and ensure that the results of the assessment are made available to the relevant representative or committee who may comment thereon.

    (3)  When making the assessment, the employer or self­employed person shall keep a record of the assessment and take into account such matters as-

(a) the HCS to which an employee may be exposed;

(b) what effects the HCS can have on an employee;

(c) where the HCS may be present and in what physical form it is likely to be;

(d) the route of intake by which and the extent to which an employee can be exposed; and

(e) the nature of the work, process and any reasonable deterioration in, or failure of, any control measures.

    (4)  If the assessment made in accordance with subregulation (3) indicates that any employee may be exposed, the employer shall ensure that monitoring is carried out in accordance with the provisions of regulations 6 and 7 and that the exposure shall be controlled as contemplated in regulation 10.

    (5)  An employer shall review the assessment required by subregulation (1) forthwith if-

(a) there is reason to suspect that the previous assessment is no longer valid; or

(b) there has been a change in a process involving an HCS or in the methods, equipment or procedures in the use, handling, control or processing of the HCS,

and the provisions of subregulations (2) and (3) shall apply.

Air monitoring

6.  (1)  Where the inhalation of an HCS is concerned, an employer contemplated in regulation 5 (4) shall ensure that the measurement programme of the airborne concentrations of the HCS to which an employee is exposed, is-

(a) carried out in accordance with the provisions of these regulations;

(b) carried out only after the relevant health and safety representative or relevant health and safety committee has been informed thereof and given a reasonable opportunity to comment thereon;

(c) carried out by an approved inspection authority or by a person whose ability to do the measurements is verified by an approved inspection authority;

(d) representative of the exposure of employees to the airborne HCS in accordance with the provisions of subregulation (2); and

(e) verified in accordance with the provisions of subregulation (3) if the measurements are carried out by a person who is not an approved inspection authority.

    (2)  In order to comply with the provisions of subregulation (1) (d), an employer shall-

(a) ensure that the measurement programme, in the case of a group measurement, makes provision for the selection of the number of persons for a sample to be done as contemplated in chapters 3 and 4 and Technical Appendix A of the OESSM: Provided that such sample size shall be chosen for the top 10% of the group at the 95% confidence level for an HCS with a control limit and for the top 10% of the group at the 90% confidence level for an HCS with a recommended limit; and

(b) carry out representative measurements at least every 12 months for an HCS with a control limit and at least every 24 months for an HCS with a recommended limit: Provided that whenever the control limit or recommended limit which has been prescribed for an HCS is exceeded, the provisions of regulation 10 shall apply.

    (3)  In order to comply with the provisions of subregulation (1) (e), an employer shall obtain the service of an approved inspection authority who shall, at intervals not exceeding 24 months-

(a) verify, by examining the measurement and analysis equipment of the employer and questioning the person referred to in subregulation (1) (c) regarding the carrying out of the measurement programme;

(b) carry out the measurements prescribed by subregulations (1) and (2) for any one group; and

(c) enter the results of the investigation and measurements, as contemplated in paragraphs (a) and (b) respectively, in the record required by regulation 9.

Medical surveillance

7.  (1)  An employer shall ensure that an employee is under medical surveillance if-

(a) the employee may be exposed to a substance listed in Table 3 of Annexure 1;

(b) the exposure of the employee to any substance hazardous to his or her health is such that an identifiable disease or adverse effect to his or her health may be related to the exposure, there is a reasonable likelihood that the disease or effect may occur under the particular conditions of his or her work and there are techniques to diagnose indications of the disease or the effect as far as is reasonably practicable; or

(c) the occupational health practitioner recommends that the relevant employee should be under medical surveillance in which case the employer may call on an occupational medicine practitioner to ratify the appropriateness of such recommendation .

    (2)  In order to comply with the provisions of subregulation (1), the employer shall, as far as is reasonably practicable, ensure-

(a) that an initial health evaluation is carried out by an occupational health practitioner immediately before or within 14 days after a person commences employment, where any exposure exists or may exist, which comprises-

(i) an evaluation of the employee's medical and occupational history;

(ii) a physical examination; and

(iii) any other essential examination which in the opinion of the occupational health practitioner is desirable in order to enable the practitioner to do a proper evaluation.

(b) that subsequent to the initial health evaluation contemplated in paragraph (a), the relevant employee undergoes examinations as contemplated in paragraph (a) (ii) and (iii), at intervals not exceeding two years, or at intervals specified by an occupational medicine practitioner.

    (3)  An employer shall not permit an employee who has been certified unfit for work by an occupational medicine practitioner to work in a workplace or part of a workplace in which he or she would be exposed: Provided that the relevant employee may be permitted to return to work which will expose him or her if he or she is certified fit for that work beforehand by an occupational medicine practitioner.

    (4)  The employer shall record and investigate the incident contemplated in subregulation (3) in compliance with regulation 8 of the General Administrative Regulations.

Respirator zone

8.  An employer shall ensure-

(a) that any workplace or part of a workplace under his or her control, where the concentration of an HCS in the air is, or may be, such that the exposure of employees working in that workplace exceeds the recommended limit without the wearing of respiratory protective equipment, is zoned as a respirator zone;

(b) that a respirator zone is clearly demarcated and identified by notice indicating that the relevant area is a respirator zone and that respiratory protective equipment as contemplated in regulation 11 must be worn there; and

(c) that no person enters or remains in a respirator zone unless he or she is wearing the required respiratory protective equipment.

Records

9.  An employer shall-

(a) keep records of the results of all assessments, air monitoring, and medical surveillance reports required by regulations 5, 6 and 7, respectively: Provided that personal medical records shall only be made available to an occupational health practitioner;

(b) subject to the provisions of paragraph (c), make the records contemplated in paragraph (a), excluding personal medical records, available for inspection by an inspector;

(c) allow any person subject to formal written consent of an employee, to peruse the records with respect to that particular employee;

(d) make the records of all assessments and air monitoring available for perusal by the relevant health and safety representative or relevant health and safety committee;

(e) keep all records of assessments and air monitoring for a minimum period of 30 years;

(f ) keep all medical surveillance records for a minimum period of 30 years and if the employer ceases activities, all those records shall be handed over or forwarded by registered post to the relevant regional director; and

(g) keep a record of the investigations and tests carried out in terms
of regulation 12 (b) and of any repairs resulting from these
investigations and tests, and the records shall be kept for at least three years.

Control of exposure to HCS

10.  (1)  An employer shall ensure that the exposure of an employee is either prevented or, where this is not reasonably practicable, adequately controlled: Provided that-

(a) where there is exposure for which there is a recommended limit, the control of the exposure shall be regarded as adequate if the level of exposure is below that limit or if the relevant area is zoned and the level of exposure is reduced to below that recommended limit by means of adequate personal protective equipment only after the level has been reduced to as low as is reasonably practicable by any other means than personal protective equipment; or

(b) where there is exposure for which there is a control limit, the control of the exposure shall be regarded as adequate if the exposure is at a level as low as is reasonably practicable below that control limit: Provided that in the case of temporary excursions above the control limit, the employer shall ensure-

(i) that the excursion is without a significant risk from exposure;

(ii) that the excursion is not indicative of a failure to maintain adequate control;

(iii) that during the excursion, the area is temporarily demarcated as prescribed in regulation 8 (b); and

(iv) the provisions of regulation 11 are complied with.

    (2)  Where reasonably practicable, the employer shall control the exposure of an employee-

(a) by limiting the amount of an HCS used which may contaminate the working environment;

(b) by limiting the number of employees who will be exposed or may be exposed;

(c) by limiting the period during which an employee will be exposed or may be exposed;

(d) by using a substitute for an HCS;

(e) by introducing engineering control measures for the control of exposure, which may include the following:

(i) Process separation, automation or enclosure;

(ii) the installation of local extraction ventilation systems to processes, equipment and tools for the control of emissions of an airborne HCS;

(iii) use of wet methods; and

(iv) separate workplaces for different processes;

(f) by introducing appropriate work procedures which an employee must follow where materials are used or processes are carried out which could give rise to exposure of an employee and that procedures shall include written instructions to ensure-

(i) that an HCS is safely handled, used and disposed of;

(ii) that process machinery, installations, equipment, tools and local extraction and general ventilation systems are safely used and maintained;

(iii) that machinery and work areas are kept clean; and

(iv) that early corrective action can be readily identified .

    (3)  An employer shall ensure that the emission of an HCS into the atmosphere comply with the provisions of the Atmospheric Pollution Prevention Act, 1965 (Act No.45 of 1965).

Personal protective equipment and facilities

11.  (1)  If it is not reasonably practicable to ensure that the exposure of an employee is adequately controlled as contemplated in regulation 10, the employer shall-

(a) in the case of an airborne HCS, provide the employee with suitable respiratory protective equipment and protective clothing; and

(b) in the case of an HCS which can be absorbed through the skin, provide the employee with suitable non­HCS impermeable protective equipment.

    (2)  Where respiratory protective equipment is provided, the employer shall ensure-

(a) that the relevant equipment is capable of controlling the exposure to below the OEL for the relevant HCS;

(b) that the relevant equipment is correctly selected and properly used;

(c) that information, instructions, training and supervision which is necessary with regard to the use of the equipment is known to the employees; and

(d) that the equipment is kept in good condition and efficient working order.

    (3)  An employer shall, as far as is reasonably practicable-

(a) issue no used personal protective equipment to an employee, unless the relevant protection equipment is decontaminated and sterilised;

(b) provide separate containers or storage facilities for personal protective equipment when not in use; and

(c) ensure that all personal protective equipment not in use is stored only in the place provided therefor.

    (4)  An employer shall as far as is reasonably practicable, ensure that all contaminated personal protective equipment is cleaned and handled in accordance with the following procedures:

(a) Where the equipment is cleaned on the premises of the employer, care shall be taken to prevent contamination during handling, transport and cleaning;

(b) where the equipment is sent off the premises to a contractor for cleaning purposes-

(i) the equipment shall be packed in impermeable containers;

(ii) the containers shall be tightly sealed and have clear indication thereon that the contents thereof are contaminated; and

(iii) the relevant contractor shall be fully informed of the requirements of these regulations and the precautions to be taken for the handling of the contaminated equipment.

    (5)  Subject to the provisions of subregulation (4) (b), an employer shall ensure that no person removes dirty or contaminated personal protective equipment from the premises: Provided that where contaminated personal protective equipment has to be disposed of, it shall be treated as HCS waste as contemplated in regulation 15.

    (6)  Subject to the provisions of the Facilities Regulations, an employer shall, where reasonably practicable, provide employees using personal protective equipment as contemplated in subregulation (1), with-

(a) adequate washing facilities which are readily accessible and located in an area where the facilities will not become contaminated, in order to enable the employees to meet a standard of personal hygiene consistent with the adequate control of exposure, and to avoid the spread of an HCS;

(b) two separate lockers separately labelled "protective clothing" and "personal clothing", and ensure that the clothing is kept separately in the, locker concerned; and

(c) separate "clean" and "dirty" change rooms if the employer uses or processes an HCS to the extent that the HCS could endanger the health of persons outside the workplace.

Maintenance of control measures

12.  An employer shall ensure-

(a) that all control equipment and facilities provided in terms of regulations 10 and 11, are maintained in good working order; and

(b) that thorough examinations and tests of engineering control measures are carried out at intervals not exceeding 24 months by an approved inspection authority or by a person whose ability to do the measurements and tests is verified by an approved inspection authority.

Prohibitions

13.  No person shall as far as is reasonably practicable-

(a) use compressed air or permit the use of compressed air to remove particles of an HCS from any surface or person; or

(b) smoke, eat, drink or keep food or beverages in a respirator zone or permit any other person to smoke, eat, drink or keep food or beverages in that zone.

Labelling, packaging, transportation and storage

14.  An employer shall, in order to avoid the spread of contamination of an HCS, take steps, as far as is reasonably practicable, to ensure-

(a) that the HCS in storage or distributed are properly identified, classified and handled in accordance with SABS 072 and SABS 0228;

(b) that a container or a vehicle in which an HCS is transported, is clearly identified, classified and packed in accordance with SABS 0228 and SABS 0229; and

(c) that any container into which an HCS is decanted, is clearly labelled with regard to the contents thereof.

Disposal of hazardous chemical substances

15.  An employer shall as far as is reasonably practicable-

(a) recycle all HCS waste;

(b) ensure that all collected HCS waste is placed into containers that will prevent the likelihood of exposure during handling;

(c) ensure that all vehicles, re­usable containers and covers which have been in contact with HCS waste are cleaned and decontaminated after use in such a way that the vehicles, containers or covers do not cause a hazard inside or outside the premises concerned;

(d) ensure that all HCS waste which can cause exposure, is disposed of only on sites specifically designated for this purpose in terms of the Environmental Conservation Act, 1989 (Act No. 73 of 1989), in such a manner that it does not cause a hazard inside or outside the site concerned;

(e) ensure that all employees occupied in the collection, transport and disposal of HCS waste, who may be exposed to that waste, are provided with suitable personal protective equipment; and

(f) ensure that if the services of a waste disposal contractor are used, a provision is incorporated into the contract stating that the contractor shall also comply with the provisions of these regulations.

Offences and penalties

16.  Any person who contravenes or fails to comply with any provision of regulation 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 shall be guilty of an offence and liable on conviction to a fine or to imprisonment for a period not exceeding six months and, in the case of a continuous offence, to an additional fine of R200 for each day on which the offence continues or additional imprisonment of one day for each day on which the offence continues: Provided that the period of such additional imprisonment in no case exceeds 90 days.

Short title

17.  These regulations shall be called the Regulations for Hazardous Chemical Substances,1995.

Annexure 1
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OCCUPATIONAL HEALTH AND SAFETY ACT, 1993
HCS Guidelines

Prevention and control of exposure

1.  Exposure of employees to substances hazardous to health should be prevented or, where this is not reasonably practicable, adequately controlled. This is a fundamental requirement of the Regulations for Hazardous Chemical Substances (HCS), 1995. Exposure can occur by inhalation, ingestion or absorption through the skin, but inhalation is usually the main route of entry into the body. Tables 1 and 2 of Annexure 1 list the occupational exposure limits which should be used in determining the adequacy of control of exposure by inhalation, as required by the HCS Regulations.

2.  The advice in this document should be taken in the context of the requirements of the HCS Regulations, especially regulation 5 (Assessment of potential exposure), regulation 10 (Control of exposure), regulation 12 (Maintenance of control measures) and regulation 6 (Air monitoring). Substances hazardous to health are defined in regulation 1. There is separate legislation for lead and asbestos and these substances are not covered in detail in this document. This document also does not apply to exposure below ground in mines or exposure to micro­organisms.

3.  Adequate control of exposure (when prevention is not reasonably practicable) should be achieved by one or more of a range of control measures described in regulation 10 of the HCS Regulations. Control by personal protective equipment should be applied only when other means are not reasonably practicable.

Medical surveillance

4.  Medical surveillance of employees is often an important addition to the control measures in the workplace. Regulation 7 (1) of the HCS Regulations specifies where medical surveillance is appropriate for the protection of the health of employees.

4.1  Medical surveillance is defined in the Regulations to cover the spectrum of potential effects of an HCS on an employee, from absorption of the substances through to clinical disease. Medical surveillance may be grouped broadly into-

(a) biological monitoring, to measure the extent of absorption of an HCS by the employee.

(b) medical screening, to detect any adverse effects of an HCS on the employee.

4.2  Biological monitoring of exposure

4.2.1  Objectives

Biological monitoring of exposure can be divided into two types of testing:

(a) Biological monitoring: Measures the biochemical concentrations of HCSs and/or their metabolites in biological samples of exposed individuals, e.g. blood lead for inorganic lead exposure, or urinary arsenic for inorganic arsenic exposure. The aim is to measure the degree of absorption into the body by measuring indicators in representative biological samples, typically urine or blood (usually not related to the target organ).

(b) Biological effect monitoring: Determines the intensity of biochemical or physiological change due to exposure, e.g. red cell cholinesterase for exposure to organosphosphate pesticides, or zinc protoporphyrin (ZPP) for exposure to inorganic lead.

4.2.2  Uses of biological monitoring

Biological monitoring tests are indices of an individual's exposure and they may be a useful tool for the occupational health and safety team. They give information on the overall level of exposure, regardless of whether an HCS has been absorbed by the respiratory, oral, or cutaneous route. Cutaneous absorption can play a significant role in the case of some organic compounds. The amounts absorbed through the skin may be comparable to or even higher than those absorbed via the respiratory tract.

Where appropriate, environmental control measures may thus be supplemented, with biological monitoring. Knowledge of the real individual exposure permits targeted applications of preventive measures.

4.2.3  Important considerations in biological monitoring

(a)  In choosing a test to meet the above objectives, it is important to have an understanding of the relationship between environmental exposure and the concentration of an HCS in biological samples. This includes an understanding of the principles of absorption, biotransformation, distribution and excretion of an HCS.

(b)  In addition, there should be analytical methods available of sufficient sensitivity and specificity to detect concentrations of the substance in urine, blood or exhaled air in the range likely to be encountered in industry.

(c)  The HCSs listed in Table 3 of Annexure 1 are those for which the above criteria have a reasonable change of being met.

4.2.4  Biological Exposure Indices (BEIs)

BEIs are reference values intended as guidelines for the evaluation of potential health hazards in the practice of industrial hygiene. A BEI represents in theory the level of an HCS or metabolite most likely to be observed in a specimen collected from a healthy worker who has been exposed to an HCS to the same extent as the worker with inhalation exposure to an OEL­TWA. BEIs do not represent a sharp distinction between hazardous and non­hazardous exposures. For example, owing to biological variability, it is possible that an individual's measurements can exceed the BEI without incurring an increased health risk. Conversely, there may be some susceptible individuals who may be harmed at effects below the BEI.

If measurements in specimens obtained from a worker on different occasions persistently exceed the BEI, or if the majority of measurements in specimens obtained from a group of workers at the same workplace exceed the BEI, the cause of the excessive values must be investigated and proper action be taken to reduce the exposure.

BEIs apply to eight­hour exposures, five days a week. However, BEIs for differing work schedules may be extrapolated on pharmacokinetic grounds. BEIs should not be applied either directly or through a conversion factor, in the determination of safe levels for non­occupational exposure to air and water pollutants, or food contaminants. The BEIs are not intended for use as a measure of adverse effects or for diagnosis of occupational illness.

4.3  Medical screening

4.3.1  Objectives

(a) The principle of general medical screening is to detect a disease at an early subclinical or presymptomatic stage in order to take action to reverse these effects or to slow progression of the disease. The abnormalities sought, include pathophysiological or histopathological changes. Such tests are well established in general preventative medicine, e.g. PAP smears for cervical cancer, cholesterol screening, faecal occult blood for lower bowel cancer, etc.

(b) In medical surveillance in industry one is interested not only in detecting adverse effects in the individual, but also in the implication of the findings for the effectiveness of workplace control measures. Medical surveillance is thus directed not only at early adverse effects but also at established disease.

4.3.2  Types of examination

(a) The number of validated screening tests with regard to HCSs is smaller than in general preventive medicine, but is likely to grow in the future. Examples of subclinical tests include urinary cytology for bladder cancer among workers exposed to potential bladder carcinogens, or full blood counts for employees exposed to an HCS toxic for the bloodforming organs.

(b) Medical surveillance may include simple clinical examination, such as examination of the skin of employees exposed to contact irritants or allergens, or of the nasal septum of employees exposed to chromates.

(c) Chest X­rays for silicosis are an example of screening for irreversible (although potentially progressive) disease. Lung function testing is well established as a non­specific test for the possible effect of respiratory irritants, sensitisers and fibrogenic agents.

4.4  Designing and implementing a programme of medical surveillance

4.4.1  The following steps should be included in any programme:

(a) Risk assessment to determine the potential exposure to and routes of absorption of any HCS, as required by regulation 5.

(b) Identification of target­organ toxicity, so as to direct medical screening.

(c) Selection of appropriate tests and testing schedule. Tests should have the desirable operating characteristics of high sensitivity, specificity, reliability and predictive value. The frequency of testing is laid down in general terms by regulation 7 (2), but should in any case be based on an understanding of the nature of the hazard and the natural history of any adverse effects.

(d) Development of action criteria. These are provided for some HCSs in the form of BEIs in Table 3 of Annexure 1. Criteria for interpreting lung function testing have also been published in the medical literature. However, in many cases, the occupational health practitioners will have to develop pragmatic criteria in the context of the specific workplace.

(e) Standardisation of test process. Quality control needs to be exercised both in the testing site and in the laboratory contracted to carry out analyses. Consistency over time should be sought so as to make longitudinal measurements comparable.

(f) Ethical considerations. Information and training of employees as required by regulation 3 (1) should include the rationale for doing medical surveillance, and the consequence of abnormal findings. An employee must be notified of the results and interpretation of his/her tests and any recommendations made. The confidentiality of personal medical records is laid down by regulation 9.

(g) Determination of employee's fitness to remain in that job. [Regulation 7 (3)]. Results may be compared against the action criteria (BEI if relevant), and preferably also the employee's previous results to determine whether individual action needs to be taken. Action may include repeating the test, further medical examination, removal of the employee from further exposure, and notification of the employer. Co­operation of employees can be best secured by a policy of protection of conditions of service in case of medical removal from a particular job.

(h) Evaluation of control. An abnormal finding in an employee, or a pattern of findings in a group of employees, may point to inadequate primary control of exposure. In such cases the employer needs to be notified of such details of the medical findings as are necessary to evaluate the workplace problem and take remedial action.

(i) Recordkeeping. This includes both medical records and exposure information for every employee. While the employer is responsible for recordkeeping in terms of regulation 9, the contents of personal medical records may be accessible to the occupational medicine practitioner, the employee, and any person nominated by the employee in writing.

4.4.2  The onus is on the occupational health practitioner carrying out medical surveillance to be familiar with the latest scientific information regarding the HCS and tests that might be useful. The aim should be to design a programme that is rational, ethical and effective. This may have to be done in the face of incomplete information or uncertainty regarding exposures, toxicity and test performance.

Legal background to exposure limits

5.  Two types of occupational exposure limits are defined in regulation 1 of the HCS Regulations. The two types are occupational exposure limit-control limit (OEL-CL), and occupational exposure-limit recommended limit (OEL-RL), as listed in Tables 1 and 2 of Annexure 1. The key difference between the two types of limits is that one OEL-RL is set at a level at which there is no indication of a risk to health; for an OEL-CL, a residual risk may exist and the level set, takes socio­economic factors into account. Further details are given in paragraphs 8 to 16.

6.  Regulation 10 of the HCS Regulations lays down the requirements for the use of an OEL-CL and an OEL-RL for HCS for the purpose of achieving adequate control. Regulation 10 (1) requires that, where there is exposure to a substance for which an OEL-CL is specified in Table 1 of Annexure 1, the control of exposure shall, so far as inhalation of that substance is concerned, be treated as adequate only if the level of exposure is reduced so far as is reasonably practicable and in any case below the OEL-CL.

7.  Regulation 10 (1) of the HCS Regulations requires that, where there is exposure to a substance for which an OEL-RL has been approved, the control of exposure shall, so far as inhalation of that substance is concerned, be treated as adequate if-

(a) that OEL-RL is not exceeded; or

(b) where that OEL-RL is exceeded, the employer identifies the reasons for the exceeding of the standard and takes appropriate action to remedy the situation as soon as is reasonably practicable.

Setting occupational exposure limits

Advisory council and standing technical committee

8.  OEL-RL and OEL-CL are set by the chief inspector on recommendation of the Advisory Council for Occupational Health and Safety (the Advisory Council), following assessment by the Standing Committee No. 7 (TC 7) of the Advisory Council for Occupational Health and Safety.

9.  TC 7 must first consider what type of limit is appropriate, OEL-RL or OEL-CL, and secondly, at what concentration the limit should be set. Setting an OEL-RL is the first option to be considered and TC 7 comes to a decision based on a scientific judgment of the available information on health effects. If, however, TC 7 decides that an OEL-CL is more appropriate, consideration of the level at which to set the limit passes to the Advisory Council, since it involves socio-economic judgments, balancing risk to health against the cost and effort of reducing exposure.

Following public consultation, new OEL-CLs and OEL-RLs are listed in Table 1 and Table 2 of Annexure 1 respectively with the approval of the chief inspector.

The indicative criteria

10.  An OEL-RL can be assigned to a substance, if all three the following criteria are complied with:

There is a no-risk at the exposure limit

Criterion 1: The available scientific evidence allows for the identification, with reasonable certainty, of a concentration averaged over a reference period, at which there is no indication that the substance is likely to be injurious to employees if they are exposed by inhalation day after day to that concentration.

Likely excursions above the exposure limit are unlikely

Criterion 2: Exposure to concentrations higher than that derived under criterion 1 and which could reasonably occur in practice, is unlikely to produce serious short or long­term effects on health over the period of time it might reasonably be expected to take to identify and remedy the cause of excessive exposure.

Compliance is reasonably practicable

Criterion 3: The available evidence indicates that compliance with an OEL-RL, as derived under criterion 1, is reasonably practicable.

11.  A substance which does not meet criteria 1, 2 and 3, can be assigned an OEL-CL and must meet either of the following criteria:

Criterion 4: The available evidence on the substance does not satisfy criterion 1 and/or 2 for an OEL-RL and exposure to the substance has, or is liable to have, serious health implications for workers; or

Criterion 5: Socio­economic factors indicate that although the substance meets criteria 1 and 2 for an OEL-RL, a numerically higher value is necessary if the controls associated with certain uses are to be regarded as reasonably practicable.

Setting an OEL-RL

12.  Criterion 1 sets out the fundamental basis for establishing such a limit: The existence of a threshold above which there may be evidence of significant effects on health but below which, on existing knowledge, there are thought to be no adverse effects.

13.  Criterion 2 is necessary in order to take account of HCS Regulation 10 (1) of the HCS Regulations whereby exposures above an OEL-RL are allowed provided the employer identifies the reasons for exceeding the standard and takes steps to reduce exposure to that OEL-RL as soon as is reasonably practicable. Clearly, it is necessary to take account of the likelihood and probable extent of cases in deciding whether an OEL-RL is appropriate. The health effects to be taken into account include sensory and other effects such as the slowing of reflexes which might result in the impairment of safety.

14.  Criterion 3 takes account of whether industry can reasonably comply with the exposure limit derived under the first criterion. There is no purpose in setting an OEL-RL which plainly cannot be achieved in practice. Note that industry's ability to comply, influences the decision of whether to set an OEL-RL, but does not influence the level at which that OEL-RL is set.

Setting an OEL-CL

15.  To be assigned an OEL-RL, a substance must meet all the first three criteria; if it does not, then it can be considered for an OEL-CL. To be assigned an OEL-CL, there should be serious implications for the health of workers exposed to the substance. Serious health implications include both the risk of serious health effects to a small population of workers and the risk of relatively minor health effects to a large population. In practice, an OEL-CL has been most often allocated to carcinogens and to other substances for which no threshold of effect can be identified and about which there is no doubt about the seriousness of the effects of exposure.

16.  An OEL-CL and an OEL-RL, therefore, differ not only in their legal status, but also in the way in which they are set. For an OEL-RL the only consideration in setting the limits is the protection of the health of the employee; for an OEL-CL this is still the primary consideration but socio­economic factors are also taken into account.

17.  The indicative criteria, then, provide the framework within which the discussions at the various stages of limit­setting can be conducted.

Applying occupational exposure limits

General

18.  The lists of occupational exposure limits given in Tables 1 and 2 of Annexure 1, unless otherwise stated, relate to personal exposure to substances hazardous to health in the air of the workplace.

Units of measurement

19.  In occupational exposure limits, concentrations of gases and vapours in air are usually expressed in parts per million (ppm), a measure of concentration by volume, as well as in milligrams per cubic metre of air (mg m^­3), a measure of concentration by mass. In converting from ppm to mg m^­3 a temperature of 25°C and an atmospheric pressure of 101,325 kPa are used. Concentrations of airborne particles (fume, dust, etc) are usually expressed in mg m^­3. In the case of dust, the limits in the tables refer to the total inhalable fraction unless specifically indicated as referring to the respirable fraction (see paragraph 36). In the case of a man­made mineral fibre, the limit is expressed as fibres per millilitre of air (fibres m^­1).

Occupational exposure limits - control limits: OEL-CL (table 1)

20.  An OEL-CL is the maximum concentration of an airborne substance, averaged over a reference period, to which employees may be exposed by inhalation under any circumstances, and is specified together with the appropriate reference period in Table 1 of Annexure 1.

21.  Regulation 19 (1) of the HCS Regulations, when read in conjunction with the Act, imposes a duty on the employer to take all reasonable precautions and to exercise all due diligence to ensure that exposure is kept as far below an OEL-CL as is reasonably practicable.

22.  To comply with this duty, in the case of substances with an 8­hour reference period, employers should undertake a programme of monitoring in accordance with regulation 6 so that they can show (if it is the case), that an OEL-CL is not exceeded. Such a monitoring programme need not be undertaken if the assessment carried out in accordance with regulation 5 shows that the level of exposure is most unlikely ever to exceed an OEL-CL. For substances assigned a short­term limit, such value should never be exceeded.

23.  The assessment should also be used to determine the extent to which it is reasonably practicable to reduce exposure further below an OEL-CL as required by regulation 10 (1). In assessing reasonable practicability, the nature of the risk presented by the substance in question should be weighed against the cost and the effort involved in taking measures to reduce the risk. (Also see the definition of "reasonably practicable" as defined in the Act.)

Occupational exposure limit - recommended limit: OEL-RL (table 2)

24.  An OEL­RL is the concentration of an airborne substance, averaged over a reference period, at which, according to current knowledge, there is no evidence that it is likely to be injurious to employees if they are exposed by inhalation, day after day, to that concentration.

25.  For a substance which has been assigned an OEL-RL, exposure by inhalation should be reduced to that standard. However, if exposure by inhalation exceeds the OEL-RL, then control will still be deemed to be adequate provided that the employer has identified why the OEL-RL has been exceeded and is taking appropriate steps to comply with the OEL­RL as soon as reasonably practicable. In such a case, the employer's objective must be to reduce exposure to the OEL-RL, but the final achievement of this objective may take some time. The assessment under regulation 5 will determine the urgency of the necessary action, taking into account the extent and cost of the required measures in relation to the nature and degree of exposure involved.

26.  Control of an OEL-RL as prescribed in regulation 10 (1) (a) can always be regarded as adequate control of that substance for the purposes of the HCS Regulations, so far as exposure from inhalation is concerned. However, due to the variations in process control and the fluctuations in substance concentrations in the workplace, it will be prudent for employers to reduce exposure below an OEL-RL so as to ensure that the exposure of all employees does not exceed that OEL-RL. Similarly, it is not intended that the statutory requirements under regulation 10 (1) should discourage the further application of good occupational hygiene principles in order to reduce exposure below the OEL-RL.

Long-term and short-term exposure limits

27.  The pattern of effects due to exposure to substances hazardous to health varies considerably depending on the nature of the substance and the exposure. Some effects require prolonged or accumulated exposure. The long­term (8­hour time weighted average) exposure limit is intended to control such effects by restricting the total intake by inhalation over one or more workshifts. Other effects may be seen after brief exposures which have occurred once or repeatedly. Short­term limits (usually 15 minute) may be applied to such substances. Where long­term limits also apply, the short­term limits restrict the magnitude of excursion above the average concentration during longer exposures. For those substances for which no short­term limit is specified, it is recommended that a figure of three times the long­term limit be used as a guideline for controlling short­term excursions in exposure. With some other substances, brief exposure may be critical and the exposure limit necessary to prevent these excursions will also control any other effects. A separate long­term limit is not considered necessary in such cases and the short­term limit applies throughout the shift.

28.  Exposure limits are expressed as airborne concentrations averaged over a specified period of time. The period for the long­term limit is normally eight hours. When a different period is used, this is stated. The averaging period for the short­term exposure limit is normally 15 minutes. Such a limit applies to any 15 minute period throughout the working shift.

Limitations to the application of exposure limits

29.  The exposure limits relate to personal exposure with the exception of the annual OEL-CL for vinyl chloride which should be recorded as the timeweighted average of vinyl chloride in the atmosphere of a working place over a period of one year (see Annexure 2) and the OEL-RL for cotton dust is not a personal exposure standard, but a static air standard (see Annexure 4).

30.  The limits cannot readily be extrapolated to evaluate or control non­occupational exposure, e.g. levels of contamination in the neighbourhood close to an industrial plant. OELs only apply to persons at work. Employers should also take into account their duties under the Environmental Protection Act. The OELs are also only approved for use where the atmospheric pressure is between 85 KPa and 101,325 KPa. This covers the normal range of meteorological variations and slightly pressurised workplaces such as cleaning rooms, but not the higher pressures that may be encountered in, for example, tunnelling or underwater hyperbaric chambers. Such situations require special assessments.

31.  Occupational exposure limits, as set out in Tables 1 and 2 of Annexure 1, are intended to be used for normal working conditions in workplaces. Employers should also take into account their duties and the provisions of the Environmental Conservation Act. OELs are not, however, designed to deal with serious accidents or emergencies, particularly where employees may be exposed to rapidly rising concentrations of gas, as may arise from a major escape due to plant failure. Over and above their responsibilities to ensure that the requirements of the HCS Regulations are met, employers also have a clear responsibility to ensure that the plant is designed, operated and maintained in a way that avoids accidents and emergencies. Where appropriate, detection, alarm and response measures should be used in order to minimise the effect of any such unplanned events.

32.  To help maintain adequate operational control, employers may find it helpful to select their own indicators of control when undertaking investigations or corrective action.

Exposure in mines

33.  The HCS Regulations and the occupational exposure limits in this publication do not apply to exposure to substances hazardous to health in mines.

Lead and asbestos

34.  Work with asbestos or lead is not subject to the HCS Regulations. The exposure limits for various types of asbestos and lead are specified in the Asbestos Regulations and the Lead Regulations.

Pesticides

35.  Substances used as active ingredients in pesticides are listed under their chemical names and/or their common (ISO) names. These names may sometimes be used as parts of the names of proprietary pesticide formulations. In all cases the exposure limit applies to the specific active ingredients and not to the formulation as a whole.

Dusts

36.  The general approach necessary to control occupational exposure to dusts is as follows: not all dusts have been assigned occupational exposure limits but the lack of such limits should not be taken to imply an absence of hazard. In the absence of a specific exposure limit for a particular dust, exposure should be adequately controlled. Where there is no indication of the need for a lower value, personal exposure should be kept below both 10 mg m^­3 8­hour time­weighted average total inhalable dust and 5 mg m^­3 timeweighted average respirable dust. Such, or greater, dust concentrations should be taken as the substantial concentrations. A substantial concentration of dust should be taken as a concentration of 10 mg m^­3, 8­hour time­weighted average, of total inhalable dust or 5 mg m^­3, 8­hour time­weighted average, of respirable dust, where there is no indication of the need for a lower value, and as such they are referred to as substances hazardous to health.

Total inhalable dust and respirable dust

37.  Total inhalable dust approximates to the fraction of airborne material that enters the nose and mouth during breathing and is therefore available for deposition in the respiratory tract. Respirable dust approximates to the fraction which penetrates to the gas exchange region of the lung. A fuller definition is given at the end of Table 2 of Annexure 1 (Abbreviations).

38.  Where dusts contain components which have their own assigned occupational exposure limits, all the relevant limits should be complied with.

Fume

39.  Where a separate OEL has been set for fume, it should normally be applied to solid particles generated by chemical reactions or condensed from the gaseous state, usually after volatilisation from melted substances. The generation of fume is often accompanied by a chemical reaction such as oxidation or thermal breakdown.

Absorption through the skin

40.  In general, for most substances the main route of entry into the body is by inhalation. The OELs given in these regulations solely relate to exposure by this route. Certain substances such as phenol, aniline and certain pesticides (marked in the Tables with an SK notation) have the ability to penetrate the intact skin and thus become absorbed into the body. Absorption through the skin can result from localised contamination, for example from a splash on the skin or clothing, or in certain cases from exposure to high atmospheric concentrations of vapour. Serious effects can result in little or no warning and it is necessary to take special precautions to prevent skin contact when handling these substances. Where the properties of the substances and the methods of use provide a potential exposure route via skin absorption, these factors should be taken into account in determining the adeauacv of the control measures.

Sensitisers

41.  Certain substances may cause sensitisation of the respiratory tract if inhaled or skin contact occurs. Respiratory sensitisers can cause asthma, rhinitis, or extrinsic allergic alveolitis. Skin sensitisers cause allergic contact dermatitis. Substances which cause skin sensitations are not necessarily respiratory sensitisers or vice­versa. Only a proportion of the exposed population will become sensitised, and those who do become sensitised, will not have been identified in advance. Individuals who become sensitised may produce symptoms of ill health after exposure even to minute concentrations of the sensitiser.

42.  Where it is reasonably practicable, exposure to sensitisers should be prevented. Where this cannot be achieved, exposure should be kept as low as is reasonably practicable and activities giving rise to short­term peak-concentrations should receive particular attention. As with other substances, the spread of contamination by sensitisers to other working areas should also be prevented, as far as is reasonably practicable.

43.  The Sen notation (marked in the Tables with a Sen notation) has been assigned only to those sensitisers that may cause sensitisation by inhalation. Remember that other substances not contained in these Tables can act as respiratory sensitisers.

Other factors

44.  Working conditions which impose additional stress on the body, such as exposure to ultra­violet radiation, high temperatures, pressures and humidity, may increase the toxic response to a substance. In such cases, specialist advice may be necessary to evaluate the effects of these factors.

Mixed exposures

General

45.  The majority of OELs listed in Tables 1 and 2 of Annexure 1 are for single compounds or for substances containing a common element or radical, e.g. tungsten and compounds, and isocyanates. A few of the limits relate to substances commonly encountered as complex mixtures or compounds e.g. white spirit, rubber fume, and welding fume. However, workers are frequently subject to other mixed exposures involving solids, liquids, aerosols or gases. These exposures can arise as a result of work with materials containing a mixture of substances, or from work with several individual substances, simultaneously or successively, in a workshift. Mixed exposures require careful assessment of their health effects and the appropriateness of control standards. The following paragraphs provide a brief summary of the advice on the application of exposure limits in these circumstances. In all cases of doubt, specialist advice should be sought.

Effects of mixed exposures

46.  The ways in which the constituent substances of a mixed exposure interact, vary considerably. Some mixed exposures involve substances that act on different body tissues or organs, or by different toxicological mechanisms, these various effects being independent of each other. Other mixtures will include substances that act on the same organs, or by similar mechanisms, so that the effects reinforce each other and the substances are additive in their effect. In some cases the overall effect is considerably greater than the sum of the individual effects and the system is synergistic. This may arise from mutual enhancement of the effects of the constituents or because one substance potentiates another, causing it to act in a way which it would not do alone.

Assessment and control

47.  With all types of mixed exposures, it is essential that assessments be based on the concentrations of each of the constituents in air to which workers are exposed. Depending on the nature of the consituents and the circumstances of use, the relative concentrations of the constituents in air may differ considerably from those in the liquid or solid source material. The composition of the bulk material should not be relied on for assessment unless there is good evidence for doing so.

48.  Where mixed exposure occur, the first step is to ensure adequate control of exposure for each individual substance. However, the nature and amount of the other substances in a mixture can influence the level to which it is reasonable practicable to reduce exposure to a substance subject to an OEL­CL. When limits for specific mixtures have been established, they should be used only where they are applicable, and in addition to any relevant individual limits. They should not be extended to inappropriate situations. It is then necessary to assess whether further control is needed to counteract any increased risk from the substances acting in conjunction. Expert assessments for some particular mixed exposures may be available and can be used as guidelines in similar cases. In other cases, close examination of the toxicological data will be necessary to determine which of the main types of interaction (if any) are likely for the particular combination of substances concerned. The various types should be considered in the following order:

(a) Synergistic substances: Known cases of synergism and potentiation are considerably less common than the other types of behaviour in mixed exposures. However, they are the most serious in their effects and require the most strict control. They are also the most difficult to assess and wherever there is reason to suspect such interaction, specialist advice should be obtained;

(b) Additive substances: Where there is reason to believe that the effects of the constituents are additive, and where the exposure limits are based on the same health effects, the mixed exposure should be assessed by means of the formula-

      C₁/L₁+C₂/L₂+C₃/L₃....... <1

here C₁, C₂, etc are the time­weighted average (TWA) concentrations of constituents in air and L₁, L₂, etc are the corresponding exposure limits. The use of this formula is only applicable where the additive substances have been assigned OELs, and L₁, L₂, etc. relate to the same reference period in the list of approved OELs. Where the sum of the C/L fractions does not exceed one, the exposure is considered not to exceed the national OELs. If one of the constituents has been assigned an OEL-CL, then the additive effect should be taken into account in deciding the extent to which it is reasonably practicable to further reduce exposure; and

(c) Independent substances: Where no synergistic or additive effects are known or considered likely, the constituents can be regarded as acting independently. It is then sufficient to ensure compliance with each of the OELs individually.

49.  The above steps provide basic protocol for assessment of mixed exposures. It is open to persons responsible for control of exposure to treat all nonsynergistic systems as though they were additive. This avoids the need to distinguish additive and independent systems and can be regarded as the more prudent course, particularly where the toxicity data are scarce or difficult to assess.

Monitoring mixed exposure

50.  Further information on monitoring airborne contaminants is given in paragraphs 52 and 53. The number of components of a mixed exposure for which routine air monitoring is required, can be reduced if their relative concentrations can be shown to be constant. This involves the selection of a key or marker, which may be one of the constituents, as a measure of the total contamination. Exposure to the marker is controlled at a level selected so that exposures to all components will be controlled in accordance with the criteria in paragraphs 48 (a) and (b). However, if one of the components has been assigned an OEL-CL, the level of the exposure to that substance should always be reduced as far as is reasonably practicable. If this approach is to be used, it should take place under the guidance of suitable specialist advice.

Complicating factors

51.  Several factors that complicate the assessment and control of exposure to individual substances will also affect cases of mixed exposures and will require similar special consideration. Such factors include-

(a) exposure to a substance for which there is no established limit or for which an OEL-CL has been set;

(b) the relevance of factors such as alcohol, medication, smoking and additional stresses;

(c) exposure of the skin to one or more substances that can be absorbed by this route, as well as by inhalation; and

(d) substances in mixture may mutually affect the extent of their absorption, as well as their health effects, at a given level of exposure.

Monitoring exposure

52.  Regulation 5 (4) of the HCS Regulations imposes a duty on the employer to monitor the exposure of employees to substances hazardous to health.

53.  Details of routine sampling strategies for individual substances are outside the scope of this document. However, advice is available in EH 42, which provides practical guidance on monitoring substances hazardous to health in air.

TABLE 1

OCCUPATIONAL EXPOSURE LIMITS - CONTROL LIMITS FOR HAZARDOUS CHEMICAL SUBSTANCES

**Vinyl chloride is also subject to an overriding annual TWA OEL-CL of 3 ppm.

TABLE 2

OEL-RL: OCCUPATIONAL EXPOSURE LIMIT -
RECOMMENDED LIMIT FOR HAZARDOUS CHEMICAL SUBSTANCES

* The OEL-RL for aluminium does not include exposure to aluminium coated with mineral oil, or to fume arising from aluminium welding processes.