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Workplace Exposure Limits (WEL): COSHH Regulations Explained

12 July 2024

Bethan Stones headshot

Bethan Stones

Group Marketing Manager

Cura Terrae

What are Workplace Exposure Limits?

Nearly all industry regulated by the Health and Safety Executive (HSE) is affected in some way by the COSHH regulations. For example, those using paints in the coating of manufactured products, solvents in the printing industries, silica and metals used in foundries, wood dust in furniture production and disinfectant type chemicals used to clean medical instruments in hospitals.

Under Regulation 7 of the COSHH regulations, it is stated that Control Of Exposure may only be treated as adequate if any Workplace Exposure Limits (WEL) for that substance is not exceeded. Therefore employers have a duty to ensure each of their employees is not exposed to any concentration of substance in excess of the Workplace Exposure Limits for that substance.

The WEL value is expressed as a time weighted average (TWA) and there are two variations, the Long Term Exposure Limit (LTEL) which is the maximum exposure permitted over an 8-hour period and the Short Term Exposure Limit (STEL) which is the maximum exposure permitted over a 15-minute reference period.

The LTEL is designed to protect the workforce from concentrations of contaminant, which over a large period of time could cause long term chronic ill health effects. Whereas the STEL exposure limit relates to peak exposure incidents and is designed to protect against immediate acute ill-health effects.

Workplace Exposure Limits are approved by the Health and Safety Commission (HSC) acting on advice given from the Advisory Committee on Toxic Substances, (ACTS) which in turn act on scientific and technical advice given by Working Group on Action to Control Chemicals (WATCH).

Due to the large amount of chemical compounds used in the workplace there is insufficient information available on many of these to warrant quantifiable exposure limits to be in place. Consequently not all chemicals used in the workplace have WEL values. New substances are added and existing ones can be revised and are published in new additions or supplements to the Health and Safety Executives EH40 Booklet.

Experts in Workplace Exposure Limits

In order to assist you in preparing an up to date COSHH Assessment, the most effective way of assessing exposure levels to substances in the workplace is by portable air sampling. A popular way of doing this is by drawing a known quantity of air through a sorbent tube, which is then analysed for contaminants known to be used in the process. Samples can be fitted to operatives over the course of a day to determine personal exposure. Following sampling we can assess current working practices and suggest means of preventing or reducing exposure to hazardous substances by improving safety measures (protective equipment, PPE) and control strategies, such as Local Exhaust Ventilation (LEV).

Measurement should be carried out at regular intervals, when processes change, when new plant or materials are introduced, or when new information comes to light regarding the substances used, such as a new or revised WEL.

Call us on 01274 738668 or fill out our Envirocare Enquiry Form for any queries regarding Workplace Exposure Limits, COSHH Risk Assessments, Air Monitoring or LEV.