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Polychlorinated Biphenyl Transformer Incident -- New Mexico

On June 17, 1985, a transformer located in the basement of the New Mexico State Highway Department building in Santa Fe was found to have overheated and released an oily mist containing polychlorinated biphenyls (PCBs) and their pyrolysis by-products. The transformer contained 245 gallons of askarel*, most of which was vented from the transformer. The askarel was tested for PCBs, and the result was interpreted as negative. Therefore, clean-up began under the assumption that PCBs were not present. By that afternoon, however, a laboratory identified PCBs in an askarel fluid sample from the site. By that time, the three-story building had been extensively contaminated, compounded in part by the clean-up efforts.

Contamination occurred in several ways: (1) mist containing PCBs and pyrolysis by-products entered two rooms in the basement adjacent to the transformer vault and two rooms on the ground floor above the vault via vents and unsealed electrical conduits; (2) direct spread of mist and fumes occurred through three stairwells located in the building, none of which had fire doors; (3) air drafts created by open windows and exhaust fans spread fumes throughout the building; (4) foot traffic by employees and emergency-response teams extended the contamination; (5) the exhaust vent in the transformer room, located near the intake vents for the building's air-conditioning system, allowed further contamination through fumes drawn into the air-conditioning system.

The askarel contained 87% polychlorinated biphenyl (PCB) (Aroclor 1260**) and a mixture of tri- and tetra-chlorinated benzenes (13%). Air samples obtained within 14 hours after the incident showed PCB levels of 48 ug/m((3)) in the transformer vault and 20 ug/m((3)) in the room above the vault. Wipe samples of surfaces showed PCB levels ranging from 30 million ug/m((2)) for grossly contaminated surfaces to 4,700 ug/m((2)) for a desk top with no visible contamination.***

Additional air and surface samples were collected June 22-24. Analysis of these samples demonstrated potential pyrolysis products of PCBs and polychlorinated benzenes. The 2,3,7,8 isomer of tetrachlorodibenzofuran (TCDF) was identified in concentrations averaging 48 pg/m((3)) of air in the most heavily contaminated areas of the building. For wipe samples, levels ranged from 41,224 ng/m((2)) on grossly contaminated surfaces to 5 ng/m((2)) in areas with no visible contamination. The 2,3,7,8 isomer of tetrachlorodibenzo-p-dioxin (TCDD) was not detectable in air samples or on surface wipes (detection limit 0.5-5.0 pg/m((3)) for air samples and 180 ng/m((2)) for surface wipes). The highest levels of chlorinated benzenes were found on the second floor, where air levels of 168 mg/m((3)) and 3.9 mg/m((3)) were recorded for 1,2,4-trichlorobenzene and 1,2,3,4-tetrachlorobenzene, respectively.

The Office of Epidemiology, New Mexico Health and Environment Department, conducted a study to determine whether exposure to fumes or oil at the transformer incident site had caused illness. Exposed persons were identified by highway department officials, by police and fire department attendance logs, and by self-reporting. A questionnaire was administered to exposed and unexposed employees and to emergency-response team members. Eighty (79.2%) of the 101 persons with known exposure completed questionnaires. The most commonly observed symptoms were: nausea (27.5%), eye irritation (22.5%), sore throat (21.2%), nose irritation (18.8%), chest tightness (15.0%), and headache (15.0%). Symptoms were transient and usually resolved as soon as the person left the site. However, two people reported headaches persisting more than 1 day. Nine persons were evaluated at a local emergency room and then released. Analysis of symptom-prevalence data showed that, for individuals not wearing self-contained breathing apparatuses, the number of symptoms was correlated with time at the site (r = 0.236, p = 0.039) and time in the building (r = 0.340, p = 0.035).

Fifty-six persons with known exposure submitted sera for PCB analysis, as did 20 controls (unexposed firefighters and highway department employees). Serum PCBs were calculated using Aroclor 1260 as the standard. All but four persons had levels below 10 parts per billion (ppb). The median for exposed persons was 4.1 ppb (range 1.2-41.8 ppb) compared to 2.4 ppb (range 0.9-8.0 ppb) for controls. The values observed in exposed persons were greater than in controls (p 0.002). Persons who entered the building had higher serum PCB levels than persons exposed to fumes outside (median: 4.8 ppb inside; 3.4 ppb outside; p = 0.014). Neither individual symptoms nor total numbers of symptoms were correlated positively with serum PCB level.

The affected building has not been reopened. Reported by K Sherrell, RF Meyerhein, MS, Organics Section, Scientific Laboratory Div, SA Rogers, MES, WT Slade, MES, C Oppenheimer, Occupational Health and Safety Bureau, D Fort, Environmental Improvement Div, HF Hull, MD, State Epidemiologist, New Mexico Health and Environment Dept; Div of Field Svcs, Epidemiology Program Office, Div of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, CDC.

Editorial Note

Editorial Note: According to Environmental Protection Agency estimates, approximately 77,600 PCB transformers were being used in or near commercial buildings at the end of 1984 (e.g., office buildings, hospitals, schools, and shopping centers) (1). While past attention has focused mainly on spills of PCBs from this equipment, the recent occurrence of several fires (2,3) involving PCB-containing transformers has focused attention on what may be a more important threat to public health: fires resulting in widespread contamination of structures with PCBs and, in some cases, polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs), including 2,3,7,8-TCDD. In addition to these soot-producing incidents, release of PCBs from the pressure-relief valves of overheated transformers have also resulted in contamination. Although a previous incident of this type did not result in detected concentrations of PCDFs and PCDDs (4), the Santa Fe incident demonstrates that significant formation of PCDDs and PCDFs, including 2,3,7,8-TCDF can occur from overheated transformers. The formation of PCDFs and PCDDs from the pyrolysis of electrical fluids is of paramount concern as some of the congeners are much more toxic than PCBs. Groups at risk from these exposures include firefighters and other emergency-response personnel, clean-up workers, and occupants of these structures.

In experimental animal studies, exposure to PCB, PCDFs, and PCDDs at a wide range of exposure concentration may cause various systemic effects, including immunologic dysfunction and teratogenesis. In addition, PCBs and TCDDs are carcinogenic in rats and mice (5,6). Humans exposed to PCBs, TCDDs, or PCDFs have developed chloracne, metabolic disorders, and other systemic problems (5,6). Epidemiologic studies of humans chronically exposed to PCBs or PCDDs in the workplace suggest an association between exposure to these compounds and increased incidence of cancer (7-9). However, the long-term health effects of acute exposure, such as this, are not known.


  1. Environmental Protection Agency. Federal Register, Part IV. 1985;50:29170-201.

  2. O'Keefe PW, Silkworth JB, Gurthy JF, et al. Chemical and biological investigations of a transformer accident at Binghamton NY. Environmental Health Perspect 1985;60:201-9.

  3. DesRosiers PE. PCB's, PCDF's, and PCDD's resulting from transformer/capacitor fires: an overview. In: Addis G, Komai RY, eds. Proceedings: the 1983 PCB seminar, EPRI EL-3581, project 2028. Palo Alto, California: Electric Power Research Institute, 1984;6-41 to 6-57.

  4. National Institute for Occupational Safety and Health. Health hazard evaluation report no. HETA 82-310-1475. Cincinnati, Ohio: National Institute for Occupational Safety and Health, 1984.

  5. National Institute for Occupational Safety and Health. Criteria for a recommended standard: occupational exposure to polychlorinated biphenyls (PCBs). Cincinnati, Ohio: National Institute for Occupational Safety and Health, 1977; DHEW publication no. (NIOSH) 77-225.

  6. National Institute for Occupational Safety and Health. Current intelligence bulletin no. 40: 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, "dioxin"). Cincinnati, Ohio: National Institute for Occupational Safety and Health, 1984; DHHS publication no. (NIOSH) 84-104.

  7. Brown DP, Jones M. Mortality and industrial hygiene study of workers exposed to polychlorinated biphenyls. Arch Environ Health 1981;36:120-9.

  8. Urabe H, Koda H, Asahi M. Present state of Yusho patients. Annals New York Academy of Sciences 1979;320:273-6.

  9. Hardell L, Sandstrom A. Case-control study: soft tissue sarcomas and exposure to phenoxyacetic acids or chlorophenyls. Brit J Cancer 1979;39:711-7. *Fire-resistant, electrically insulated coolant liquid used in PCB transformers. **Use of trade name is for identification only and does not imply endorsement by the U.S. Department of Health and Human Services and the Public Health Service.

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