[Influencing factors on urinary chromium levels of occupational population]

To investigate the possible factors affecting the total urinary chromium levels on a group of hexavalent chromium(Cr(Ⅵ)) occupational population in a chromate production factory, which will provide the scientific basis for workers' health promotion and self-protection.

In May 2021, a cross-sectional study was conducted in a chromate production enterprise, in that, the demographic information, occupational history, past disease history as well as life style concerning the Cr(Ⅵ) exposed group(n=651) which cover the roasting, manufacturing, refining, chromic anhydride, power and overhauling sectors and the control group(n=74) which are all from functional department were collected through a questionnaire survey, the ambient Cr(Ⅵ) exposure levels either catched from a short-time detection pattern(C_(STE)) at certain work places or sampled from a series of typical posts throughout the main processes by aiming at the time-weight average exposure levels(C_(TWA)) for 8 h. The pre-shift urinary samples(5-10 mL) of all participants were collected and the total Cr(Ⅵ) levels were determined by the graphite atomic absorption spectroscopy method. Kruskal-Wallis test was used to analyze the concentration of hexavalent chromium in air and urine in different workshops. The possible factors who influencing the total Cr(Ⅵ) levels were analyzed by the multiple linear regression.

There were 448 males and 203 females in the exposed group, with an average age of 44.25 and 43.39 years old, respectively, and an average length of service of 8.61 and 9.14 years, respectively. There were 32 males and 42 females in the control group, with an average of 37.22 and 35.5 years old, respectively, and an average length of service of 6.88 and 7.5 years, respectively. The urinary chromium level in the exposed group(M(P25, P75)) was 3.05(1.09, 8.70) μmol/mol creatinine, with 8 individuals exceeding the biological exposure limit in urine(1.2%), while the urinary chromium level in the control group was all less than 0.22 μmol/mol creatinine. Age(F=65.82, P<0.01), gender(χ~2=19.97, P<0.01), working-age(F=5.55, P<0.05), smoking(χ~2=5.58, P=0.02) and weekly cumulative working hours(χ~2=100.77, P<0.01) were statistically significant at different urinary chromium levels. the C_(TWA )of the 6 chromium-contacting job positions met the occupational exposure limit(PC-TWA 0.05 mg/m~3), but the air chromium concentration(0.010 mg/m~3) and urinary chromium(18.60(7.07, 27.41)μmol/mol creatinine) in the chromic anhydride section were significantly different from those in other sections(P<0.01). The multivariate linear regression indicated that variables of age and the ambient Cr(Ⅵ) concentrations were noted to contribute to the total urinary chromium levels with significant differences(P<0.05).

The ambient Cr(Ⅵ) concentrations at workplaces throughout the main processes in this chromate factory is an important factor affecting the workers' total urinary chromium levels, and the change of chromium anhydride workshop is the most significant.