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Legal Limits on Air Pollution: COSHH Regulations

We are exposed to air pollution every day, both outdoors and in our homes. The third major source of air pollution is the workplace. Exposure to harmful dust, fumes and gases can cause short-term health problems like eye irritation and dermatitis. In the longer term, exposure to hazardous substances in the workplace may lead to chronic health problems, like occupational asthma, sick building syndrome, and even cancer. Fortunately, there is a legislative framework in place in the UK which is intended to protect employees' health in the workplace.

Contact us today for expert advice: 020 3051 7826


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The Control of Substances Hazardous to Health (COSHH) Regulations (2002) require employers to control any substances present in the workplace which could be hazardous to health. Most workplaces will use, or maybe create, such substances. Exposure to a hazardous substance can occur through breathing, skin contact, injection into the skin, and swallowing. The law also applies to self-employed people if they may expose others to a hazardous substance during the course of their work.

The Health and Safety Executive (HSE) provides a wealth of information and support on COSHH.

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The Workplace Exposure Limit (WEL) is the maximum allowable concentration of a hazardous substance in the air, averaged over a period of time. The short-term WEL is the WEL over 15 minutes, while the long-term WEL is the average over 8 hours. Both must be adhered to by employers. The WEL for a particulate substance is given in mg/m3 while that for gas or vapour is given in parts per million (ppm).

The list of WELs, which covers around 500 hazardous substances, was last updated on December 2011. Many thousands of substances are used in the workplace and we do not know nearly enough about their biological effects. Just because a substance does not have a WEL defined does not mean it is safe. However, the work of REACH (see below) will increase our database of knowledge about the hazards of chemicals used in the workplace and by the consumer. We may, therefore, find new substances added to the list of those which have WELs.

The WEL list notes when a substance is carcinogenic causes asthma or is absorbed through the skin (if this is known). Exposure to any substance that causes cancer, asthma or genetic damage must be kept to an absolute minimum under COSHH.

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The broad categories of hazardous substances are:

  • Chemicals
  • Dust
  • Vapours
  • Microorganisms
  • Gases


Note, there are separate regulations on lead, radioactivity and asbestos so these do not fall under COSHH.

Some of the substances you may have heard of that have a WEL include:

  • Carbon black
  • Cotton Dust
  • Carbon monoxide
  • Flour dust
  • Grain Dust
  • Hardwood and softwood dust
  • Cement dust
  • Silica
  • Xylene


Dust of any kind (whether or not its components have a WEL) also has a WEL. The inhalable fraction must not exceed 10 mg/m3 and the respirable fraction must not exceed 4 mg/m3. Inhalable means dust particles getting into the nose and mouth and can, therefore, get into the lungs. Respirable means the fraction of this that actually gets into the gas exchange section of the lungs.

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First of all, the employer needs to know what health hazards might be present in the workplace(s) they are responsible for. Are there processes that emit dust, fumes, vapours, mist or gas? What jobs or tasks lead to exposure? Are substances that the HSE has given a WEL present in your workplace? These questions are the starting point for making your COSSH assessment (and there is plenty of guidance from the Health and Safety Executive, with examples of the level of detailed planning needed). An assessment is needed for each potentially hazardous substance, which involves deciding how harm is to be prevented. Whatever the control measures needed (e.g. adequate ventilation, specialised storage), they must be provided, used, and kept in order. Where WELs are involved, levels have to be monitored to provide backup data on exposure levels.

Employees will need information, instruction and training. Sometimes health monitoring and surveillance will also be necessary. This is the case when it is known that specific disease, like cancer or asthma, is associated with exposure to a particular substance. The employer will also need to plan for emergencies, such as leaks of solvent or gas escapes.

Remember, prevention at source is best - so, can you avoid the use of a hazardous substance altogether by substituting it, or using a different process or approach?

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Failure to comply with COSHH regulations is a crime punishable by fine and leaving the employer open to civil claims. The HSE along, with the local authority, enforces COSHH under the Health and Safety Act. There have been around 500 prosecutions per annum over the last few years under the Act, most of them successful (not all relating to COSHH, however, as there are other reasons why a health and safety law may be invoked).

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This is assuming that there is no alternative to using a hazardous substance. In such cases, employer and employee work together to minimise exposure, based upon the information and advice they have from their risk assessment and safety data sheet. The employer can:

  • arrange for total or partial enclosure of the hazardous substance
  • ensure good ventilation around the premises
  • install a local exhaust ventilation system to clean the air and protect people from inhalation
  • provide personal protective equipment, such as respirators, masks, and gloves
  • provide an update training in storing and handling hazardous substances


The employee can protect themselves from a hazardous substance by regulating and monitoring their behaviour when carrying out tasks and procedures. Make sure you understand the safety data sheet and risk assessment and always behave accordingly.

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REACH stands for Registration, Evaluation, Authorisation and restriction of Chemicals and is a complex, and still evolving (being phased into 2018), a piece of European legislation which aims to provide more information about known hazardous substances, and those that are potentially hazardous. REACH covers chemicals used in the workplace and also those used in consumer products. Manufacturers making large quantities of substances (10 or more tonnes per annum) need to register and will have to provide more information about their products which will be passed down the supply chain. The scheme should result in more detailed safety data sheets and information on potential exposure scenarios and advice on risk assessment. Employers should understand where they stand in the supply chain and their responsibilities under REACH.

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According to the HSE, COSHH and REACH 'sit together'. While COSHH has its WELs as a guideline, in REACH there is a Derived No Effect Level (DNEL) for a substance. The manufacturer or importer uses the DNEL to identify correct risk management measures (RMM) and also exposure scenarios for various tasks and procedures. This information appears on the REACH Safety Data Sheet. If this guidance is followed, then an employer will comply with the DNEL (which is more of a benchmark than an exposure limit). At the same time, if employers stick with COSHH guidelines, they will comply with WELs. COSHH guidelines and RMM under REACH ought to match up. If they do not (for instance, suppose the RMM in the safety data sheet does not seem to apply to what you are doing) then the employer needs to provide feedback to the supplier.

Speak to one of the experts at Commercial Air Filtration to discover the right solution to ensure legal compliance: 020 3051 7826.


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