Workplace exposure limits
Changes to workplace exposure limits: EH40 update
SOCOTEC outlines the EH40 update and provides an understanding of the new workplace exposure limits and why they are fundamental to ensuring appropriate changes can be put into place to improve regulation compliance and to safeguard the health of employees.
From 21 August 2018, the third edition of HSE’s guidance document ‘EH40/2005 Workplace Exposure Limits’ came into force, introducing new and revised workplace exposure limits for 31 substances.
The updates to EH40/2005 have been made to include recommendations from the European Agency for Safety and Health at Work (EU-OSHA) in its fourth list of Indicative Occupational Exposure Limit Values (IOELV).
With the health of workers at the focus, the list of IOELVs relate to the risks of chemical agents in the workplace. Using the most recent scientific data available and taking into account the availability of reliable measurement techniques, the IOELV’s are health-based aiming to protect workers.
Workplace exposure limits (WELs) outline the highest acceptable concentration of an airborne hazardous substance in the workplace. In the amended EH40 document, new WEL entries for nitrogen dioxide and nitrogen monoxide, as well as a reduced WEL for the existing carbon monoxide limit, have been put into place, therefore affecting any organisation assessing exposure to Diesel Engine Exhaust Emissions (DEEEs).
Workplace exposure limits TWA
These compounds’ WELs are listed under the current EH40 version as follows:
The European Commission recognises that there may be technological challenges and associated costs for the underground mining and tunnelling industries across Europe in complying with the proposed limit values for nitrogen monoxide, nitrogen dioxide and carbon monoxide. In recognition of the challenges in these industries the Directive includes an extended transitional period until 21 August 2023 during which Member States may apply national limit values for these three substances in these industries (EH40, 2018, page 7).
Other compounds that have been revised include the new short-term exposure limit for sulphur dioxide which is present in emissions from motor vehicles (although modern low sulphur fuels normally have minimal levels). Diacetyl, a chemical used in food and manufacturing industries, has also been revised.
With WEL amendments to 31 substances, a full list of WEL revisions and additions can be found on the Health and Safety Executive (HSE) website in the EH40 document. Understanding the updated WELs will enable organisations to take appropriate actions to ensure compliance with the changes to legislation and safeguard the health of employees.
Understanding Workplace Exposure Limits
WELs are important in managing activities which use or generate hazardous substances and for undertaking risk assessments. As per Control of Substances Hazardous to Health (COSHH) Regulation 10, exposure monitoring via personal air sampling may be required to determine whether or not exposure levels are acceptable.
It is important to keep in mind that workplace exposure limits are not fine lines between safe and unsafe and these were never intended to be absolute standards. In all cases, the principles of good practice for the control of exposure to hazardous substances must be met (COSHH Schedule 2A). Where an exposure threshold for safe use cannot be established (which is the case for some carcinogens and sensitisers), then the question for adequate control cannot be conclusively addressed by compliance with an exposure limit. In this case, an ALARP approach should be taken – ensuring exposure is ‘as low as reasonably practicable’.
Keep in mind also that many WELs apply to substances that are inhaled, although exposure is also possible through ingestion, skin absorption or eye contact. All routes must be considered when assessing adequate control of exposure to a hazardous substance.
Harmful effects of DEEE
With diesel used as a major source of fuel for diesel powered vehicles, equipment and power generators, monitoring diesel engine exhaust emissions (DEEE) exposure is fundamental – and a legal requirement under COSHH Regulations 2012 – HahAZwhere employees may be exposed to the inhalation of harmful diesel engine exhaust emissions (should the risk assessment indicate this monitoring is required).
Diesel engine exhaust emissions contain a complex mixture of combustion products including gases, vapours, aerosols and particulates. The main components are oxides of nitrogen, carbon dioxide and carbon monoxide – among other substances – and the inhalation of these by-product compounds can be hazardous to human health. Trace quantities of unburned or partially oxidised diesel fuel may also result in the production of aldehydes, volatile organic compounds, and polycyclic aromatic hydrocarbons. Some of these compounds are classed as blood poisons and, in high enough concentrations, can quickly starve the body of oxygen, leading to asphyxiation. Chronic exposure to DEEE can also have a long-term impact on health, with diesel engine exhaust classed as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC).
Exposure to exhaust-polluted air can cause irritation of the eyes and the respiratory tract which is the primary health effect associated with exposure to diesel engine exhaust emissions. This is particularly notable wherever there are high levels of white smoke present in the workplace. Exposure to DEEEs, in particular blue or black smoke, can also lead to coughing and breathlessness.
Monitoring diesel engine exhaust emissions exposure
Knowing if your organisation is above or below the outlined WEL can only be done through personal exposure monitoring – but DEEEs are complex. As COSHH does not state a specific exposure limit for DEEE, organisations are reliant on the WELs outlined in EH40/2005 for individual chemicals that comprise DEEE.
Personal exposure monitoring must to be undertaken regularly to ensure that WELs are not exceeded. This can be carried out for DEEE exposure via real-time measurements and active long term sampling. Real-time monitoring while engines are in operation can identify spikes in the levels of combustion gases to help determine whether remedial actions are needed to lower exposure levels. Laboratory analysis of personal exposure samples can detect the presence of other hazardous substances present in DEEE via long term sampling (this is normally several hours within the working day).
The carbon particles in diesel exhaust are produced during combustion. Many hazardous substances from the combustion process can be adsorbed onto these carbon particles. Diesel exhaust particulate contains two main components, organic carbon (OC) and elemental carbon (EC); with OC associated with adsorbed organic substances and EC being associated with the soot cores. When assessing exposure to DEEEs, determining the EC concentration is considered an appropriate monitoring method. This substance acts as a surrogate as it is very fine and behaves much like most other DEEE gases and vapours i.e. an elevated EC concentration indicates high concentrations of these other components.
One well recognised method for sampling diesel particulates is using a cyclone sampler with quartz filter and subsequent analysis for respirable carbon. There is no WEL for EC in the UK but guidance values are available. When monitoring DEEEs, SOCOTEC applies the more cautious lower limit for EC exposure at 0.1 mg/m3.
It is crucial to note, especially with the updates to EH40/2005 guidance, that that there is not a direct correlation between EC particulates and the concentration of carbon monoxide or oxides of nitrogen (see HSE document RR252). The exposure to these gases should therefore be measured using other methods (real-time data-logging gas measurement instruments).
SOCOTEC normally proposes DEEE exposure monitoring by sampling for respirable carbon and combustion gases including carbon monoxide, nitrogen monoxide and nitrogen dioxide. Carbon dioxide levels may also be determined as a ventilation indicator.
Should the DEEE exposure level be expected to be elevated and/or ventilation expected to be poor, then it would also be recommended that the suite of analysis extends to include polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), and aldehydes.
Consequences of non-compliance
For organisations operating in industries that use or generate hazardous substances, understanding the new workplace exposure limits is fundamental to ensure appropriate changes can be put into place to improve regulation compliance and to safeguard the health of employees.
Failing to comply with regulations may allow workers to be exposed to hazardous substances at consequential levels, a subsequent ill workforce resulting in productivity loss as well as hefty fines and prosecutions. Therefore, employers must apply good occupational hygiene practices and should implement adequate exposure prevention or control measures.
The regulations may seem daunting but compliance can be made easy and understandable with the help of an occupational hygienist. SOCOTEC has a widespread team of occupational hygienists qualified to advise on regulatory requirements, develop monitoring strategies, undertake workplace exposure monitoring, local exhaust ventilation testing and help guide companies to meet their statutory duties. SOCOTEC’s occupational hygienists have extensive experience in DEEE monitoring for a wide range of clients based in rail and transport, mining, logistics, construction and manufacturing.
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