Fate and Transport in the Environment
Methods for Monitoring in the Environment
Methods for Measuring Human Exposure
Strategies for Preventing or Controlling Exposure
PCBs - Harmful Effects
PCBs - Dose Response
Sites of Toxicity
Mechanisms of Toxicity
Links for More Information
PCBs Harmful Health Effects
In 1958, Dr. Roy Hertz described the steroid cycle, anticipating what we now call endocrine disrupter research, as follows: . . . we have to consider that the introduction of . . . [hormones into cattle feed lots] leads to the exposure . . . of individuals who might otherwise not ever in their lives come in contact with such materials . . . . This is not a theoretical consideration because we . . . now have encountered two families, each with two children, who presented with simultaneously developing gynecomastia attributable to the accidental contamination of vitamin capsules by estrogens during manufacture. If such estrogens can, by stray handling, get into such pharmaceutical preparations, can they not very readily get where they are not wanted on the farm? There is one additional consideration in this regard . . . The fecal excretion of these materials . . . will be dropped on the soil and . . . over generations there will be constant replenishment of the soil surface with steroidal substances of this kind. This in turn has its effect potentially on surface water-supply contamination and also potentially on the vegetable content of steroids in crops raised on such soil . . . .I think that we are now actually setting up a steroid cycle in our environment, and we have to give very serious consideration to its implications for our subsequent development and growth and possibly reproductive functions. The above excerpt was taken from Korach et al (1). Since 1958, many research studies have been conducted that supports Dr. Hertzs hypothesis. Endocrine Disrupting Chemicals (EDCs), have now been linked to many adverse health outcomes. This site focuses on polychlorinated biphenyls (PCBs), a group of widespread persistent environmental contaminants and their impact on human health, specifically the endocrine system.
PCBs can mimic or block the action of hormones from the thyroid and other endocrine glands. Because hormones influence the normal functioning of many organs, some of the effects of PCBs may result from endocrine changes. Through these various interactions in the body, PCBs have been associated with multiple adverse health effects. Most of the human studies have many shortcomings, which make it difficult for scientists to establish a clear association between PCB exposure levels and health effects. This site examines data pertaining to both human and animal studies. The information that is available in humans is from studies of people exposed occupationally, by consumption of contaminated rice oil in Japan (the Yusho incident) and Taiwan (the Yu-Cheng incident), by consumption of contaminated fish and other food products of animal origin, and via general environmental exposures. The following is a brief description of the Yusho and Yu-Cheng occurrences
Yusho Accident, 1968 Japan
In June, 1968 patients appeared at the Dermatology clinic of Kyusthu University Hospital, Fukuoka, Japan suffering from chloracne. After few clinical, chemical and epidemiological investigations, it was found that the disease originated from the consumption of a batch of rice oil supplied in February, 1968; the disease was called Yusho (rice oil disease). This rice oil was found contaminated with Kanechlor 400, a 48% chlorinated biphenyl, at 2000-3000 mg/kg, which entered the oil through a leak in the heat exchanger. Chlorinated dibenzofurans at 5 mg/kg were found in three samples of toxic rice oil that contained PCB levels of about 1000 mg/kg (Nagayama et.al., 1976).
The earliest symptoms of PCB's exposure were enlargement and hyper-secretion of the Meibonian glands of the eyes, swelling of the eyelids and pigmentation of the nails and mucous membranes, occasionally associated with fatigue, nausea and vomiting. This was followed by hyperkeratosis and darkening of the skin with follicular enlargement and acneform eruptions. These skin changes were most often seen on the neck and upper chest, but in severe cases, extended to the whole body.
Biopsy skin samples showed hyperkeratos i.e. dilation of the follicles, and an accumulation of melanin in the basal cells of the epidermis; melanin granules have also been observed in biopsy samples of the conjunctiva, oedema of the arms and legs was also observed in some patients. The majority of the patients were found to have respiratory symptoms and suffered from chronic bronchitis like disturbance, that persisted for several years.
Yusho patients did not appear to suffer from central nervous effects, but some complained of numbness of the arms and legs. Nuco-cutaneous signs had decreased year-by-year, but neurological signs, respiratory signs and symptoms and various complaints, as general fatigue, anorexia, abdominal pain and headache, had become more prominent among the patients.
Yu-Cheng Accident, 1979 - Taiwan
A similar incident to Yusho accident occurred in Taiwan in 1979, and by the end of 1980, the number of affected persons were found 1843. The incident has been referred to as Yu-Cheng (Chang et.al., 1980a, b; Chen et.al., 1980). The accident had occurred due to the consumption of rice bran oil contaminated with PCBs that was used as a heat transfer medium in the manufacture of the oil. PCB intake was estimated to be 0.7-1.84 g and blood PCB levels ranged from 3 to 1156 µg/litre. The formation and hypersecretion of the meibonian glands occurred in patients, whose blood PCBs concentration was above 40 µg/litre.
The common symptoms noticed were heavy pigmentation of conjunctiva, abnormal cystic acneiform eruptions and follicular accentuation, skin and nail pigmentation, swelling of the eyelids and increased discharge from the eyes, headache, nausea, and numbness of the limbs. The major blood disorders were decreased hemoglobin concentration, erythrocyte conc., gamma-immunoglobin and increased white blood cell counts
In the two Asian episodes, exposure to PCBs occurred through the consumption of rice oil that had become contaminated by heat-degraded PCBs during processing. Unlike usual PCB mixtures, the Yusho and Yu-Cheng mixtures were heated in thermal heat exchangers during the cooking process, resulting in contamination of the oil by chlorinated dibenzofurans as well as PCBs. This co-contamination created controversy about the extent to which the physiologic effects observed in the Yusho and Yu-Cheng populations can legitimately be attributed to PCBs, as opposed to the dibenzofuran co-contaminants. A more complete discussion of the health effects associated with the Yusho and Yu-Cheng incidents can be found in the ATSDR toxicological profile on CDFs (ATSDR 1994) and CDDs (ATSDR 1998), and reviews by Hsu et al. (1994) and Masuda (1994).
The most commonly observed health effects in humans exposed to large amounts of PCBs are skin conditions such as acne and rashes. PCBs may also cause irritation of the nose and lungs, depression and fatigue, liver, thyroid, dermal and ocular changes, immunological alterations, neurodevelopmental changes, reduced birth weight, reproductive toxicity, and cancer. PCBs are not known to cause birth defects. The Department of Health and Human Services (DHHS) has concluded that PCBs may reasonably be anticipated to be carcinogens. The EPA and the International Agency for Research on Cancer (IARC) have determined that PCBs are probably carcinogenic to humans.
Animals that ate food containing large amounts of PCBs for short periods of time had mild liver damage, with some observed deaths. Other animal studies examining lose dose/long term exposure showed rats developing anemia; acne- like skin conditions; and liver, stomach, and thyroid gland injuries. Rats that ate food containing high levels of PCBs for two years developed liver cancer. Additional effects caused by PCBs in animals include reductions in the immune system function, behavioral alterations, and impaired reproduction.
A summary on the existing information on health effects of PCBs is presented in this graph (taken from the Seagrant web site listed below).
Examples of harmful effects of PCBs on human and animal endocrine systems will be explained in Sites of Toxicity. For additional information about animal and human health effects, please see the following web sites.
Korach KS, Sarver P, Chae K, McLachlan JA, McKinney JD. 1988. Estrogen receptor-binding activity of polychlorinated hydroxybiphenyls: conformationally restricted structural probes. Molecular Pharmacology
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