Implications for occupational exposure to particulate matter

The demonstrated effects of lower levels of ambient particles on cardiovascular and respiratory system morbidity and mortality were initially surprising in light of current concepts of occupational particle exposure and acute and chronic cardiopulmonary effects. Specifically, the exposure levels, as defined by the weight of the particles per liter of breathing air, at which recognized disease occurs under workplace conditions are considerably higher than the observed levels of ambient particles associated with serious adverse health effects. The possible reasons for this difference have not been adequately addressed. To further address this question, a re-examination of workplace exposure-response relationships is needed, which may include emphasis on measuring exposures to fine and ultrafine particles rather than to total particle mass concentration alone.