CHAPTER 2-132: POLYCHLORINATED BIPHENYLS (PCBs)

INTRODUCTION

Polychlorinated biphenyls (PCBs) are mixtures of up to 209 different chlorinated compounds that once were used widely as high-temperature insulators for transformers and other electric equipment. They were also found in carbonless copy papers, inks, paints, caulks, sealants and ceiling tiles. Many commercial PCB mixtures are known in the United States by the trade name Aroclor. Since 1974, all uses in the United States have been confined to closed systems. Most PCB poisonings are chronic occupational or environmental exposures, with delayed-onset symptoms the first indication that an exposure has occurred. In 1977, the US Environmental Protection Agency (EPA) banned further manufacturing of PCBs because they are suspected carcinogens and highly persistent in the environment. Exposure occurs through the consumption of meat, fish, and dairy because of biomagnification up the food chain, as well as by inhalation in contaminated indoor or outdoor environments. PCBs were widely used in building materials from 1950s to 1979, and remain present in buildings that were constructed or renovated during that period. Since many schools in use today were built or renovated during that era, they present a potential risk of exposure to children and staff.

MECHANISM OF TOXICITY

PCB metabolites may induce DNA strand breaks, resulting in cellular injury. PCBs are irritating to mucous membranes. When burned, PCBs may produce the more highly toxic polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs [Dioxins]). PCBs, and particularly the PCDD and PCDF contaminants, are mutagenic and teratogenic and are considered human carcinogens by the International Agency for Research on Cancer.

TOXIC DOSE

PCBs are either oily liquids or solids that are colorless to light yellow. Some can exist as a vapor in air. PCBs have no known smell or taste. PCBs are well absorbed by all routes (skin, inhalation, and ingestion) and are widely distributed in fat; bioaccumulation occurs even with low-level exposure.

1. Inhalation. PCBs are mildly irritating to the skin at airborne levels of 0.1 mg/m³ and very irritating at 10 mg/m³. The ACGIH-recommended workplace limits (TLVTWA) are 0.5 mg/m³ (for PCBs with 54% chlorine) and 1 mg/m³ (for PCBs with 42% chlorine) as 8-hour time-weighted averages. The air level considered immediately dangerous to life or health (IDLH) for either type is 5 mg/m³.

2. Ingestion. Acute toxicity after ingestion is unlikely; the oral 50% lethal dose (LD₅₀) is 1–10 g/kg.

CLINICAL PRESENTATION

1. Acute PCB exposure may cause skin, eye, nose, and throat irritation.

2. Chronic exposure may cause chloracne (cystic acneiform lesions predominantly found on the face, posterior neck, axillae, upper back, and abdomen); the onset usually occurs 6 weeks or longer after exposure. Skin pigmentation, porphyria, elevated hepatic transaminases, and thyroid hormone abnormalities may occur.

3. Epidemiologic studies suggest that PCB exposure is associated with decreased IQ and other neurobehavioral effects ...