Watchtower PCB contamination:
http://www.clearwater.org/news/pcbhealth.html
PCBs are a probable human carcinogen.
The International Agency for Research on Cancer and the Environmental Protection Agency classify PCBs as a probable human carcinogen. The National Toxicology Program has concluded that PCBs are reasonably likely to cause cancer in humans. The National Institute for Occupational Safety and Health has determined that PCBs are a potential occupational carcinogen.
Studies of PCBs in humans have found increased rates of melanomas, liver cancer, gall bladder cancer, biliary tract cancer, gastrointestinal tract cancer, and brain cancer, [1] and may be linked to breast cancer. PCBs are known to cause a variety of types of cancer in rats, mice, and other study animals. [2]
EPA´s regulations on cancer-causing chemicals use the term `probable´ when a chemical is known to cause cancer in animals and where there is evidence that suggests that it causes cancer in humans but which is not conclusive. Because you can´t feed chemicals to humans to see how they respond, it is much more difficult to demonstrate carcinogenicity in humans than in animals. Instead, studies are undertaken of groups who have been exposed to a chemical, and if they suffer from more cancers than would be expected at normal levels, this may indicate that the chemical was a carcinogen. However, there are many difficulties doing these studies: small numbers of people known to be exposed to a chemical; the fact that people suffer from many cancers without any chemical exposure; the fact that in some cases these people were exposed to a number of other chemicals; and the need to demonstrate high cancer rates that cannot be random in order to draw conclusions. Thus the term `probable´ reflects the limited nature of the studies, and it is rare that a carcinogen is so effective that it can be called a `known´ human carcinogen.
The fact that PCBs are called a `probable´ carcinogen should not be taken as a sign that they are benign.
Acute toxic effects.
People exposed directly to high levels of PCBs, either via the skin, by consumption, or in the air, have experienced irritation of the nose and lungs, skin irritations such as severe acne (chloracne) and rashes, and eye problems. [3]
PCBs cause developmental effects.
Women exposed to PCBs before or during pregnancy can give birth to children with significant neurological and motor control problems, including lowered IQ and poor short-term memory.
A group of children in Michigan whose mothers had been exposed to PCBs were found to have decreased birth weight and head size, lowered performance on standardized memory, psychomotor and behavioral tests, and lowered IQ. These effects lasted through at least 7 years. [4] A group of women occupationally exposed to PCBs in upstate New York had shorter pregnancies and gave birth to children with lower birth weight. [5]Another study, of the chidren of women who ate contaminated Lake Ontario fish, found significant performance impairments on a standardized behavioral assessment test. [6]
Exposure of one form of PCB to rats resulted in retarded growth, delayed puberty, decreased sperm counts, and genital malformations. [7] In other studies, exposure of PCBs to rats in utero led to behavioral and psychomotor effects that lasted into adulthood. [8]
PCBs disrupt hormone function.
PCBs with only a few chlorine atoms can mimic the body´s natural hormones, especially estrogen. Women who consumed PCB-contaminated fish from Lake Ontario were found to have shortened menstrual cycles. [9]PCBs are also thought to play a role in reduced sperm counts, altered sex organs, premature puberty, and changed sex ratios of children. More highly-chlorinated PCBs (with more chlorine atoms) act like dioxins in altering the metabolism of sex steroids in the body, changing the normal levels of estrogens and testosterone. [11] PCBs tend to change in the body and in the environment from more highly-chlorinated to lower-chlorinated forms, increasing their estrogenic effects.
Immune system and thyroid effects.
In a study of adolescents Mohawk males in New York State, PCBs were shown to upset the balance of thyroid hormones, which may affect growth as well as intellectual and behavioral development. [12]
Like dioxin, PCBs bind to receptors that control immune system function, disturbing the amounts of some immune system elements like lymphocytes and T cells. [13]
In a study of Dutch children, PCB levels were tied to an increased prevalence of ear infections and chickenpox and with lowered immune system function, and thus greater susceptibility to disease. [14]
Why are PCBs called a `probable´ carcinogen?
https://en.wikipedia.org/wiki/Polychlorinated_biphenyl
A polychlorinated biphenyl (PCB; CAS number 1336-36-3 ) is a synthetic organic chemical compound of chlorine attached tobiphenyl, which is a molecule composed of two benzene rings. There are 209 configurations of organochlorides with 1 to 10 chlorine atoms. The chemical formula for a PCB is C12H10−xClx. 130 of the different PCB arrangements and orientations are used commercially.[1]
Polychlorinated biphenyls were widely used as dielectric and coolant fluids, this means that they reduce the chance of fires occurring in electrical fields in such a manner that is safe for electricians to work with. For example in electrical apparatus, cutting fluids for machining operations, carbon paper and in heat transfer fluids.[2] Due to PCBs' environmental toxicity and classification as a persistent organic pollutant, PCB production was banned by the United States Congress in 1979 and by the Stockholm Convention on Persistent Organic Pollutants in 2001.[3] According to the U.S. Environmental Protection Agency (EPA), PCBs cause cancer in animals and are probable human carcinogens.[4]
Concerns about the toxicity of PCBs are largely based on compounds within this group that share a structural similarity and toxicmode of action with dioxin. Toxic effects such as endocrine disruption and neurotoxicity are also associated with other compounds within the group. The maximum allowable contaminant level in drinking water in the United States is set at zero, but due to water treatment technologies, a level of 0.5 parts per billion is the de facto level.[5]