Occupational asthma with low level exposure

I have been told that I can't have occupational asthma as the isocyanate levels at work are always at safe levels, is this true? Meredith SK, Bugler J, Clark RL, Isocyanate exposure and occupational asthma: a case-referent study, Occup Environ Med, 2000;57:830-836, Tarlo SM, Liss GM, Dias C et al, Assessment of the relationship between isocyanate exposure levels and occupational asthma, Am J Ind Med, 1997;32:517-521,

Occupational Asthma, Specialist, 7/21/2011, 7/21/2011,

Isocyanates are the commonest cause of occupational asthma recognised in many western countries. Although the risks are higher when exposurer levels are higher, there is good evidence that occupational asthma can be caused by isocyanates in workplaces where measurements of exposure to isocyanates have been within the recommended limits. A study of 27 workers with TDI asthma compared their exposure with unaffected workers from the same workplace (Meredith 2000. There were no differences in average exposures between cases and controls which well well below all exposure limits at 1.5ppb. There was evidence of increasing risk of asthma in those with exposures over 1.125 ppb (the average exposure of the controls). The relative risk for exposures over this level was 3.2 (most time-weighted exposure limits are between 5 and 20 bbb). In Canada Tarlo showed that companies employing workers with isocyanate asthma compensated by the state more often came from workplaces where statutory exposure measurements exceeded 5ppb. However 57% of those with TDI asthma and 60% of those with MDI asthma came from workplaces where all exposure measurements had been below the exposure standard of 5ppb. These observations fit in with clinical experience where isocyanate asthma is seen in workplaces where processes leading isocyanate exposure are very unlikely ever to result in levels over 5ppb.

7/21/2011