Dr Lisa Bushby discusses how the Control of Substances Hazardous to Health Regulations 2002 apply to arsenic and its compounds.
Arsenic and its compounds exhibit different levels of toxicity. While in its inorganic form, arsenic is classified as a Class 1 Carcinogen, meaning it is a substance known to cause cancer on the basis of human experience. Organoarsenicals are generally considered less toxic.
The metallic form of arsenic (As) is classified as toxic and dangerous to the environment.
COSHH applies to arsenic and its compounds.
Regulation 7(2) of COSHH specifies substitution of carcinogenic substances and processes with less hazardous ones where reasonably practicable. Where substitution is not feasible, dutyholders are required to control exposure adequately.
Adequate control means bringing the exposure within the workplace exposure limit (WEL). As outlined in EH40, arsenic and its compounds (except arsine) have a WEL of 0.1mg/m3 for long-term exposure over an eight-hour time weighted average (TWA) period. Arsine has a WEL of 0.05ppm, or 0.16mg/m3 for long-term exposure over an eight-hour TWA.
Regulation 7(5) of COSHH sets out clear requirements for the control of carcinogenic substances, including a requirement that exposure is reduced to as low a level as is reasonably practicable using methods outlined in the principles of good practice referred to in the Approved Code of Practice to the regulations.
Occupational exposure to arsenic
As arsenic exists naturally in the environment and is distributed in the air, water and land, so non-occupational exposure to arsenic is possible. Additional exposure to arsenic can be through dietary sources (predominantly fish and seafood and rice grains and rice-based products) or occupational sources.
In terms of occupational exposure to inorganic arsenic, this may occur in various industries, such as refining or smelting of metal ores, microelectronics, pesticide manufacture or application, semiconductor manufacturing, glass production, wood preservation, joinery, battery manufacturing, and working in power plants that burn arsenic-rich coal. It is also possible that workers in waste management and landfill sites may be exposed to arsenic.
Dermal and ingestion routes of exposure are possible, but the primary route of occupational exposure is through inhalation of dust or fumes.
The immediate symptoms of acute arsenic poisoning include vomiting, abdominal pain and diarrhoea, irritation of the nose and eyes, skin damage and inflamation. These are followed by numbness and tingling of the extremities, muscle cramping and ultimately death in extreme cases.
The first symptoms of long-term chronic exposure (approximately five years) to high levels of inorganic arsenic are usually observed in the skin, and include pigmentation changes, skin lesions and hard patches on the palms and soles of the feet (hyperkeratosis). However, these symptoms may be a precursor to skin cancer.
In addition to skin cancer, long-term exposure to arsenic may also cause cancers of the bladder and lungs.
Other adverse health effects that may be associated with long-term ingestion of inorganic arsenic include developmental effects, neurotoxicity, diabetes and cardiovascular disease.
Guidance on safe use
The essential principles of working with arsenic are as follows.
Design and operate processes and activities so as to minimise the risk of its emission, release and spread. In addition, as arsenic is dangerous to the environment, emissions from ventilation or work process equipment should be checked to ensure they comply with environmental protection legislation. In some cases it will be necessary to make modifications to the process equipment to reduce emissions to acceptable levels.
Take into account all relevant routes of exposure, ie skin absorption and ingestion as well as inhalation when developing control measures.
Control exposure by measures that are proportionate to the health risk.
Choose the most effective and reliable control options which minimise the escape and spread of arsenic. Use in a fume cupboard or glove box wherever possible.
Where adequate control of exposure cannot be achieved by other means, provide, in combination with other control measures, suitable personal protective equipment, including a properly-fitted, air-purifying or air-fed respirator that complies with an approved standard if a risk assessment indicates this is necessary. Respirator selection must be based on known or anticipated exposure levels and the safe working limits of the selected respirator.
Check and regularly review all elements of control measures for their continuing effectiveness.
Inform and train all employees on the hazards and risks from the substances they work with and the control measures developed to minimise risks.
Ensure that the introduction of control measures does not increase the overall risk to health and safety.
Employees should wash their hands, forearms and face thoroughly after handling arsenic or its compounds, before eating, smoking and using the lavatory and at the end of the working period. Appropriate techniques should be used to remove potentially contaminated clothing. Contaminated clothing should be washed before reuse. Eyewash stations and safety showers should be close to the workstation location.
Safety eyewear complying with an approved standard should be used when a risk assessment indicates this is necessary to avoid exposure to liquid splashes, mists, gases or dusts.
Chemical-resistant, impervious gloves complying with an approved standard should be worn at all times when handling arsenic or its compounds if a risk assessment indicates this is necessary. Verify that the gloves used are appropriate for the use of solvated arsenic for the solvent.
Regulation 7(5) of COSHH prescribes the following specific measures for employers to limit exposure to carcinogens.
Totally enclosing the process and handling systems, unless it is not reasonably practicable.
Prohibiting eating, drinking and smoking in areas that may be contaminated by carcinogens.
Cleaning floors, walls and other surfaces at regular intervals, and whenever necessary.
Designing those areas and installations which may be contaminated by carcinogens and using suitable and sufficient warning signs.
Storing, handling and disposing of carcinogens safely, including closed and clearly-labelled containers.
The generation of arsenic waste should be avoided or minimised wherever possible. Disposal should comply with the requirements of environmental protection and waste disposal legislation.
Appendix 1 of the Approved Code of Practice to the regulations also outline additional control measures for reducing exposure, including:
minimising quantities used
changing the physical form of the substance, eg from powder to solution
using a totally enclosed system or automation of the process to physically separate workers from the process
where total exposure or automation is not possible, using partial enclosure and appropriate local exhaust ventilation
providing appropriate chemical storage, including the use of closed/sealed containers, and recognition that it may be better to store one large quantity of a substance in a controlled manner than to deal with frequent supplies of smaller amounts
correctly labelling substances/materials
restricting areas of use/storage with identifying warning signs to designate their boundaries
correctly labelling and storage of all waste carcinogenic products in a secure area and providing removal by a specialist waste contractor
minimising the number of employees working in restricted areas and excluding non-essential personnel
taking precautions against contamination, including prohibiting eating, drinking and applying cosmetics in contaminated areas
providing appropriate warning signs to demarcate such areas
providing adequate washing and welfare facilities
monitoring of levels of exposure at regular and frequent intervals to ensure that WELs are not exceeded and control measures are adequate
recognising that the use of personal protective equipment can only be used as a secondary control in combination with other controls.
In addition, consider that work surfaces may become contaminated (eg fume cupboard surfaces, balances, etc) and should be wet wiped on a regular basis.
Last reviewed 15 October 2013