Serum concentrations of polychlorinated dibenzo-p-dioxins among users of ball clay

Background/Objectives: Natural contamination of ball clay with polychlorinated dibenzo-p-dioxins (PCDDs) was discovered in 1997. Reported average TEQ in ball clay has ranged up to 1500 pg/g. As many as 13.4 million adults in the US may have recreational contact with ball clay. No studies have attempted to assess blood levels of PCDDs among users of ball clay. We characterized serum TEQ due to PCDDs among ceramicists and compared this with the general population. Methods: Ceramicists were recruited from two sources: long-term (>10 years) ceramicists who were members of the Michigan Ceramics Arts Association, and current employees of a local commercial ceramic company. Study participants completed a self-administered questionnaire about diet, employment, demographics and clay practices. A 40 mL blood sample was drawn from each participant and was analyzed for 7 PCDD congeners and adjusted for lipid content. Results: Among long-term ceramicists (n=13) the mean duration of clay use was 32 years; among the commercial workers (n=14) the mean duration of clay use was 6 years. Serum TEQ of study subjects was compared to the control population of the University of Michigan Dioxin Exposure Study using published regression models adjusted for age, smoking, sex, breast feeding and BMI. Using all 27 subjects, or using long-term ceramicists and commercial workers separately, the mean serum TEQ concentrations were not elevated above background levels. Conclusion: Results from a convenience sample of long-term ceramicists and commercial ceramics workers show no evidence of significant absorption of PCDDs despite long-term contact with ball clay.