Polychlorinated naphthalene concentrations in human serum caused by unintentional production and emissions, and potential effects of polychlorinated naphthalenes on thyroid hormones

The concentrations of 75 polychlorinated naphthalene (PCN) congeners in 95 human serum samples from the Fengjiang electronic waste dismantling area and Huangyan District in Taizhou City (Zhejiang Province, China) were determined. Thyroid hormone (FT3, FT4, TSH, and TRH) concentrations in the samples were also determined. The total PCN concentrations in the samples from Fengjiang and Huangyan were 1.29 × 104-4.28 × 105 and 8.29 × 102-6.45 × 105 pg/g lipid, respectively. The less-chlorinated (Cl1-3) PCN concentrations were relatively high in all of the samples, and the concentrations in the samples from the two areas were not significantly different. The sums of the combustion-related PCN congener concentrations were significantly higher in the samples from Fengjiang than in the samples from Huangyan, and the sums of the more-chlorinated (Cl4-8) PCNs were slightly higher in the samples from Fengjiang than in the samples from Huangyan. The relationship between the PCN concentration and age indicated that electronic waste controls have decreased human exposure to PCNs but that attention should still be paid to exposure to less-chlorinated PCNs. The main PCN congeners that contributed to the toxic equivalent concentrations were markedly different for the samples from Fengjiang and Huangyan. CN-66/67 was dominant for the Fengjiang samples and CN-10 was dominant for the Huangyan samples. Attention should be paid to the risks posed by less-chlorinated PCNs to human health. CN-1, CN-2, and CN-20 concentrations are related to human thyroid hormone levels, and the relationships between less-chlorinated PCN concentrations and thyroid hormone concentrations should be further studied.