Chemical and biological investigations of a transformer accident at Binghamton, NY

A transformer fire occurred in a state office building in Binghamton, NY on February 5, 1981. Particulates from inside surfaces of ceiling panels on 16 of the 17 floors had concentrations of polychlorinated dibenzofurans (PCDFs) ranging from < 1 part per million (ppm) to 1200 ppm while polychlorinated biphenyl (PCB) concentrations varied from 28 ppm to 23,000 ppm. In spite of the wide variations in contaminant concentrations, complete analytical data from 11 floors showed that there was a consistent PCDF/PCB ratio (0.067 ± 0.026) and also consistent PCDF isomer group distributions (tetra-CDFs, 33 ± 5%; penta-CDFs, 40 ± 3%; hexa-CDFs, 18 ± 7%; hepta-CDFs, 6 ± 3%). It was found that the particulate samples could be successfully ranked in order of their degree of chemical contamination by an in vitro bioassay. The bioassay was based on induction of keratinization or changes in morphology in mouse epithelial cells. Animal toxicology experiments were carried out with a soot sample containing a PCDF concentration which approximated the mean value found on the ceiling particulates. The single dose oral LD values of the soot and its benzene extract equivalent, each administered to female guinea pigs in 0.75% methyl cellulose, were 410 and 327 mg/kg, respectively. These results demonstrated that the soot matrix had virtually no effect on the toxicity of the chemical contaminants in the soot. Morphological alterations in liver tissues from animals receiving the soot were found after examination by electron and light microscopy. Rabbits dermally exposed to the soot and its benzene extract at 500 mg/kg showed evidence of hypertrophy of centrilobular hepatocytes. In addition the rabbits exposed to the soot extract had a local inflammatory reaction at the site of application. In a subchronic feeding experiment carried out for 90 days with guinea pigs, the lowest effect level was found with an accumulated dose of 1.2 mg soot/kg. The observed effects included salivary gland duct metaplasia and decreased relative thymus weights. Based on the chemical analysis data and literature LD values for the more toxic 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and PCDFs, it was calculated that the soot contained the equivalent of 44 ppm 2,3,7,8-tetra-CDD in terms of toxicity to guinea pigs. This was in close agreement with the value of 58 ppm derived from the acute oral toxicity experiments. Air sampling, accomplished on 8 floors in the final stages of the building cleanup, showed maximum total PCDF and 2,3,7,8-tetra-CDF concentrations of 264 and 23 pg/m, respectively.