Low Toxicity Dusts–Part 2


In my last post I discussed the evidence that suggests that the “trigger values” of 10 and 4 mg/m3 that are widely used as such by many occupational hygienists for “low toxicity dusts” where an official Workplace Exposure Limit (WEL) hasn’t been set, are probably too high to prevent ill health in workers. Despite considering the evidence, the HSE’s Advisory Committee on Toxic Substances (ACTS), has decided NOT to take any action other than to recommend an awareness raising campaign for those exposed to dusts to highlight possible risks to health. However, a number of independent experts and the Trade Unions were not happy with this decision. And following the workshop at the recent BOHS Conference in Cardiff, I’m sure that many practising occupational hygienists feel that applying limits of 10 mg/m3 for inhalable dust and 4 mg/m3  for respirable dust is no longer appropriate.

In my experience there are very few workplaces where inhalable dust exposures exceed 10 mg/m3. For most common processes, it is usually “reasonably practicable” to reduce exposure well below this level by applying common engineering controls such as containment, partial containment and well designed local exhaust ventilation. And in some cases simpler measures such as improving housekeeping or the way the job is carried out, may be enough. So I don’t think that it would be too expensive for industry to work to a lower limit. The TUC has recommended values of 2.5 mg/m3 for the inhalable fraction and 1 mg/m3 for the respirable fraction of “low toxicity” dusts as interim limits. I think these are achievable in practice for most companies if they apply industry best practice. This seems a common sense approach which would reduce the risk to health for workers exposed to these dusts.

However, there there is a problem – there are a number  of “poorly soluble dusts of limited cytotoxicity”, to use the HSE’s preferred term, for which WELs have been established using the 10 and 4 mg/m3 values . For example, aluminium oxide, barium sulphate, cellulose, graphite, gypsum starch and titanium dioxide. There’s about 20 in all. If the HSE doesn’t reduce the limits for these substances, and there is no indication that they intend to do that, it may be difficult to convince employers that they need to work to a lower level than the legal limit.

I guess the best approach would be to argue that COSHH requires that even where a limit is set, the “principles of good control practice” set out in in schedule 2a, have to be applied. In my experience, in nearly all cases where we’ve carried out dust surveys there are usually simple measures that can be taken to reduce dust levels, even when exposures are below a WEL.  So, in most cases by implementing common sense measures and established industry good practice it should be possible to reduce exposure down to the TUCs recommended levels, even for those dusts where a WEL with a higher value exists.


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