Occupational Asthma – inhalation of hexavalent chromium, nickel and cadmium mists

Occupational asthma is an allergic reaction that can occur in some people when they are exposed to substances. In electroplating and similar processes these can include hexavalent chromium compounds and nickel sulphate. These substances are called 'respiratory sensitisers' or asthmagens. They can cause a change in people's airways, known as the 'hypersensitive state'.

Not everyone who becomes sensitised goes on to get asthma. But once the lungs become hypersensitive, further exposure to the substance, even at quite low levels, may trigger an attack.

Symptoms include severe shortness of breath that can stop you from doing the simplest tasks. Imagine not being able to carry your shopping or walk up the stairs or even play with your children. Some sufferers are unable to work again.

Other symptoms include wheezing, coughing and chest tightness. The symptoms can develop right after exposure to a workplace substance. But sometimes symptoms appear several hours later, possibly at night. This can make any link with workplace activities unclear.

See the below details of research conducted by the HSE in conjunction with the Surface Engineering Association (SEA). As a result of this research both the HSE and SEA agreed to update their joint guidance in light of the conclusions of this work. These guidance sheets can be found at:

  1. Hexavalent chromium in electroplating: Prevention and Control of Chromic Acid Mist
  2. Hexavalent chromium in electroplating: Prevention and Control of Skin Exposure Risks
  3. Hexavalent chromium in electroplating: Monitoring for Exposure
  4. Nickel and Nickel Alloy Plating Operations: Controlling the Inhalation Risk
  5. Nickel and Nickel Alloy Plating Operations: Controlling the risk of skin exposure

Recent Research

The HSE has conducted recent research in partnership with the SEA. The aim was to investigate whether repeat Biological Monitoring (BM) over a period of time could be used to help drive sustainable improvements in exposure control.

Fifty-three companies engaged in nickel, hexavalent chromium and/or cadmium electroplating were visited. An occupational hygiene assessment of relevant tasks and exposure controls was conducted at each visit. BM (post shift urine sampling) was used to quantitatively assess nickel, chromium and (where used) cadmium exposures. Other measurements, such as levels of contamination of worker's hands and workplace surfaces with nickel and/or chrome, were also made to provide further information on exposure paths.

A detailed insight is provided into nickel, hexavalent chromium and cadmium exposures in electroplating. The extensive measurement programme employed allows identification of a number of tasks and worker groups with potential for exposure and provides a clear picture of the standard of exposure control achieved. This provides an improved understanding of exposure routes and allows exposure control to be better targeted.

Sustainable statistically significant reductions in exposure were achieved at the companies with the highest initial levels of urinary nickel and/or chromium. This was as a direct result of developing a better understanding of exposure pathways and implementing repeat Biological Monitoring (BM) over the lifetime of the project to provide evidence of exposure control. Reductions were in the range 30 to 40% for nickel, and 20 to 30% for chromium.

This research was published as an HSL Research Report - RR963 - Exposure to hexavalent chromium, nickel and cadmium compounds in the electroplating industry

RR963 (link above) identified knowledge gaps and areas where further statistical analysis of the data collected was required. A supplementary report examines the efficacy of gloves, the use of surfactants and local exhaust ventilation in chromium plating, and the potential for transfer of contaminants outside the workplace.

Laboratory tests and statistical analysis on gloves showed that although some glove types offer more protection than others, working practices should be arranged such that gloves are worn for splash protection only and not routinely used as a primary barrier to protect against dermal exposure to hazardous substances.

No real difference in urinary chromium levels in electroplaters can be attributed to the use of surfactants or LEV to control mist emissions from plating tanks. Either approach is capable of providing adequate exposure control provided it is properly implemented and maintained.

Published scientific literature indicates that the major route by which occupational contamination is transferred outside the workplace is on work clothing. There is clear potential for this to occur in the surface engineering industry when contaminated work wear is taken home for laundering.

The supplementary report was published as an HSL Research Report - RR1042 - Exposure to carcinogens in surface engineering: Supplementary report.


Conclusions concerning exposures and BM in the above two research reports were difficult because of the low numbers of premises now conducting this type of plating. However, there is other HSE information concerning cadmium:

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Updated: 2021-05-11