An epidemic of dermatitis at a large construction site

During 6 months in 1986, an epidemic of dermatitis occurred among more than 5600 workers at a single large construction site in the United States. To identify its cause, we used the monthly nurses' log of visits to the medical facility to characterize the outbreak by person, place, and time. Follow-up studies included a survey of carpenters and skin testing of laboratory animals. Workers were more than twice as likely to visit the medical facility for a skin-related complaint in 1986 compared with 1985 (relative rate [RR] = 2.6, 95% confidence interval [CI] 2.2-3.2). Carpenters experienced the greatest increased risk (RR = 9.7, 95% CI 5.5-17.3). We found a strong association between dermatitis and handling of fire-retardant lumber and plywood. Carpenters working only with fire-retardant lumber had a rate of dermatitis 4 times that of carpenters who worked exclusively with untreated wood (RR = 3.6, 95% CI 1.5-8.6). Carpenters who occasionally worked with fire-retardant lumber and plywood were at moderate risk (RR = 2.18, 95% CI 0.7-6.7). Although laboratory tests showed that phosphate compounds could be leached with water from the fire-retardant wood, an extract of these phosphates did not irritate the skin of laboratory animals. We concluded the epidemic was a result of handling fire-retardant lumber but could not identify the specific chemical agent. In view of the observed association, construction workers should be advised to handle this material with caution, especially in high temperature and humidity.