Biological monitoring in workers in a nitrobenzene reduction plant: haemoglobin versus serum albumin adducts

The high priority of monitoring workers exposed to nitrobenzene is a conseq uence of clear findings of experimental carcinogenicity of nitrobenzene and the associated evaluations by the International Agency for Research on Can cer. Eighty male employees of a nitrobenzene reduction plant, with potentia l skin contact with nitrobenzene and aniline, participated in a current med ical surveillance programme. Blood samples were routinely taken and analyse d for aniline, 4-aminodiphenyl (4-ADP) and benzidine adducts of haemoglobin (Hb) and human serum albumin (HSA). Also, levels of methaemoglobin (Met-Hb ) and of carbon monoxide haemoglobin (CO-Hb) were monitored. Effects of smo king were straightforward. Using the rank sum test of Wilcoxon, we found th at very clear-cut and statistically significant smoking effects (about 3-fo ld increases) were apparent on CO-Hb (P = 0.00085) and on the Hb adduct of 4-ADP (P = 0.0006). The mean 'aniline-Hb adduct level in smokers was 1.5 ti mes higher than in non-smokers; the significance (P = 0.05375) was close to the 5% level. The strongest correlation was evident between the Hb and HSA adducts of aniline (r(s) = 0.846). Less pronounced correlations (but with P values < 0.02) appeared between aniline-Hb and 4-ADP-Hb adducts (r(s) = 0 .388), between 4-ADP and 4-ADP-HSA adducts (r(s) = 0.373), and between 4-AD P-Hb and aniline-HSA adducts (r(s) = 0.275). In view of the proposal for ad ditional use of the aniline-HSA adduct for biological monitoring, particula rly in cases of acute overexposures or poisonings, the strong correlation o f the Hb and HSA conjugates is noteworthy; the ratio aniline-HSA:aniline-Hb was 1:42 for the entire cohort.