Respiratory monitoring for workers exposed to creosote or coal tar might not be doing the job, according to a group of researchers led by Dr. Jonathan Borak of the Yale School of Medicine. Borak''s team found that absorption through the skin is a much more important route of exposure.
Researchers examined a group of workers at a plant where railroad ties were heat- and pressure-treated with creosote. Levels of polycylic aromatic hydrocarbons (PAHs) measured in air samples obtained for all workers showed little or no relationship to the level of hydroxypyrene measured in urine samples. In plain English, that means that although the level of PAHs in the air might have been elevated in some areas of the facility, workers in those areas did not necessarily show high levels of chemicals in their bodies.
In fact, three workers'' air samples showed PAH levels above OSHA PELs, but when a more advanced laboratory test was used, the positive results seemed to reflect interferences, rather than actual coal tar-related substances.
Researchers found that workers whose jobs involved direct contact with coal tar had higher levels of hydroxypyrene in their urine. The findings suggest that most worker exposure to coal tar products comes from absorption through the skin, rather than from breathing airborne particles. Researchers calculated that 90 percent to 99 percent of exposure comes through the skin, rather than through the lungs.
"Traditional approaches to industrial hygiene monitoring of creosote workers seem inappropriate and inadequate," wrote researchers in the Journal of Occupational and Environmental Medicine. They said that further studies were needed to evaluate the use of urine monitoring and to set more meaningful exposure limits.
by Sandy Smith ([email protected])