Are there any workplace safety levels (e.g. OELs) for nanomaterials?

Currently no regulatory occupational exposure limit (OEL) for engineered nanomaterials has been set. However, NIOSH have proposed Recommended Exposure Limits (REL) for:

• Respirable carbon nanotubes and carbon nanofibres - worker exposure should not exceed 1.0 micrograms per cubic meter (μg/m3) as an 8-hour time-weighted average (NIOSH, 2013);
• Ultrafine (nano-scale) titanium dioxide - worker exposure should not exceed 0.3 mg/m3 as an 8-hour time-weighted average (NIOSH, 2011); and
• Pigmentary titanium dioxide (particle size greater than 100 nm) - worker exposure should not exceed 2.4 milligrams per cubic meter (mg/m3) as an 8-hour time-weighted average) (NIOSH, 2011).

In addition, a number of companies have developed in-house exposure limits. There exists a degree of variability in the suggested limits, partly due to the data set upon which the exposure limit is based, but also the nature of the derivation process including what safety factors are applied. Despite this, it is clear that certain nanoparticles may be more hazardous than larger particles of the same substance. Therefore, existing occupational exposure limits for a substance may not provide adequate protection from nanoparticles of that substance. Employers should seek to minimise worker exposure by using appropriate exposure control measures.