HSE Publishes New List of Occupational Exposure Limits for UK

This year's edition of the UK Health and Safety Executive's (HSE) list of occupational exposure limits, "EH40/2000 - Occupational Exposure Limits 2000," is now available. This year's "EH40" has been restructured to make the text easier to understand, and some new reference information on test methods and guidance has been added to the tables. A response form is included so that readers can let HSE know their views on the new format.

The booklet lists Occupational Exposure Standards (OESs) and Maximum Exposure Limits (MELs). These are used to define adequate control of exposure by inhalation to hazardous substances under the Control of Substances Hazardous to Health Regulations 1999 (COSHH).

Substances that may cause harm to health are subject to COSHH. These regulations require employers to prevent, or if this is not reasonably practicable, adequately control, employees' exposure to hazardous substances.

To help protect workers against health hazards, HSE sets occupational exposure limits. There are two types of limit: maximum exposure limits (MELs) and occupational exposure standards (OESs). A MEL is set for substances that may cause the most serious health effects, such as cancer and occupational asthma. These are substances for which no threshold level of exposure for the key health effect can be determined or for which exposure thresholds may be identified but at a concentration that is not yet routinely achievable in the workplace. COSHH requires that exposure should be reduced as far below the MEL as is reasonably practicable.

An OES is set at a level at which (based on current scientific knowledge) there is no indication of risk to the health of workers who breathe it in day after day. If exposure to a substance that has an OES is reduced at least to that level, then adequate control has been achieved.

The revisions to the lists of MELs and OESs, approved by the Health and Safety Commission (HSC), include:

• Two new MELs for benzyl chloride and furfural (2-furaldehyde).
• Three new OESs for ethyl cyanoacrylate, 2-methoxymethylethoxy propanol, and 1-methoxy propyl acetate.
• A new OES for all pentyl acetate isomers (1-pentyl acetate, 3-pentyl acetate, tert-amyl acetate, 1-methylbutyl acetate, and isopentyl acetate).
• Five revised OESs for acetic anhydride, dimethylamine, ethylamine, methyl cyanoacrylate, and 1,2,4-trichlorobenzene.
• The withdrawal of two OESs for vanadium pentoxide and bromochloromethane.
• A lower MEL for benzene, which comes into force on June 27, 2000.

Some uses in the UK for the substances with new or revised limits are outlined below:

• Benzyl chloride (MEL of 0.5 part per million in air (ppm) for an eight-hour time-weighted average (8-hour TWA) and 1.5 ppm for a short term exposure limit (STEL)) is used mainly in the manufacture of quaternary ammonium salts (used in surfactants/detergents).
• Furfural (2-furaldehyde) (MEL of 2 ppm (8-hour TWA) and 5 ppm (STEL)) is principally used in the refining of lubricating oils. Significant amounts are also used in the production of resins, abrasive wheels and refractories.
• Ethyl cyanoacrylate - OES of 0.3 ppm (STEL) - is used as an adhesive in a wide range of industries wherever a high strength, instant bond is required.
• 2-methoxymethylethoxy propanol (OES of 50 ppm (8-hour TWA)) is used in the production of coatings, cleaners, and printing inks.
• 1-methoxy propyl acetate (OES of 50 ppm (8-hour TWA) and 150 ppm (STEL)) is used in the production of coatings, cleaners, and printing inks.
• Pentyl acetates (1-pentyl acetate, 3-pentyl acetate, tert-amyl acetate, 1-methylbutyl acetate, and isopentyl acetate) (OES of 50 ppm (8 hour TWA) and 100 ppm (STEL)). The major use of 1-pentyl acetate, the most common isomer, is in flavorings and fragrances.
• Acetic anhydride (OES of 0.5 ppm (8-hour TWA) and 2 ppm (STEL)) is used by UK industry in the manufacture of cellulose acetate fibers, plastics, and vinyl acetate. It is also used as an acetylating agent or dehydrating agent in the production of pharmaceuticals, dyes, fragrances, explosives, and food additives.
• Dimethylamine (OES of 2 ppm (8-hour TWA) and 6 ppm (STEL)) is used as an intermediate in the manufacture of agrochemicals, coagulating agents, dyestuffs, resin curing agent, fabric softener, pharmaceuticals, size for paper manufacture, and in the synthesis of chemical intermediates.
• Ethylamine (OES of 2 ppm (8-hour TWA) and 6 ppm (STEL)) is used as an intermediate in the manufacture of agrochemicals, rubber curing accelerator, dyestuffs, and solder fluxes.
• Methyl cyanoacrylate (OES of 0.3 ppm (STEL)) is used as an adhesive in a wide range of industries wherever a high strength, instant bond is required.
• 1,2,4-trichlorobenzene (OES of 1 ppm (8-hour TWA)) is used mainly in the manufacture of high performance insulation for use in wire and cable products.

HSC has approved a phased reduction in the MEL for benzene from a current level of 5 ppm, to 3 ppm from June 27, 2000, and then to 1 ppm by June 27, 2003, consistent with the requirement of the first amendment to the Carcinogens Directive.

Proposals for new or revised OESs and MELs, or for their withdrawal, come from recommendations by HSC's Advisory Committee on Toxic Substances (ACTS) and its Working Group on the Assessment of Toxic Chemicals (WATCH). The draft proposals for EH40/2001 will be published in May 2000.

WATCH considered the scientific information for vanadium pentoxide and concluded that there was insufficient data to support a health-based OES. The OES has been withdrawn and the substance is being considered for a MEL. In the interim, HSE has issued a Chemical Hazard Alert Notice (CHAN).

For bromochloromethane, WATCH considered the scientific information and concluded that there was sufficient concern about carcinogenicity to withdraw the health-based OES and issue a CHAN. As both the production and use of bromochloromethane will be banned in the European Community in the near future, there are no plans to consider a MEL for this substance.

Copies of "EH40/2000 - Occupational Exposure Limits 2000," ISBN 0 7176 1730 0, price £9.50, are available from HSE Books, PO Box 1999, Sudbury, Suffolk, CO10 6FS; telephone: 01787-881165; fax: 01787-313995. Priced publications are also available through booksellers.

Edited by Sandy Smith