Medical surveillance for leukemia at a petrochemical manufacturing complex: four-year summary

Four-year results are presented on 2086 participants of a medical surveillance program of current and retired employees at a manufacturing complex in Illinois. Annual complete blood cell count testing and intensive follow-up of all out-of-normal-range results began in 1985 on a voluntary basis. The program to date has not identified any evidence for an unusual distribution of out-of-range complete blood cell count results. Active employees with out-of-range complete blood cell count values had no increase in adverse health outcomes compared with those with in-range values. Retired employees with out-of-range values were more likely to have a serious underlying medical condition, but this appeared to be more a function of age than of occupational exposure. Four cases of myelodysplastic syndrome were brought to our attention as a result of the program, but there is no similarly followed population available for comparison to determine whether this represents an increase over expected cases. The lack of correlation of out-of-range complete blood cell count results in active employees with serious hematologic disease raises significant questions about the utility of such surveillance for chemically exposed groups (eg, benzene-exposed workers) when exposure levels are low and well controlled.