Comparison of employees' white blood cell counts in a petrochemical plant by worksite and race.

To determine if employment within a petrochemical plant's quality control (QC) laboratory had any significant effect on the hematopoietic system, and in specific, the white blood cell (WBC) counts, all employees of the QC laboratory were evaluated retrospectively. Trend analysis, linear regression, and Students t tests were performed on all employees of the QC laboratory and on a simple random sample of the rest of this Caribbean petrochemical plant's male employees. Trend analyses revealed a downward trend in 82.6% of the QC laboratory workers and 76.7% in other plant workers. Linear regression and t tests revealed no statistically significant difference by worksite but a significant difference between blacks and whites. The result of the findings of the QC laboratory workers was consistent with that expected in both plant employees and the US general population. A recommendation is made that the Occupational Safety and Health Administration (OSHA) reconsider its WBC cutoff level in the benzene standard.