PCBs

Dioxins, polychlorinated dibenzo-p-dioxin (PCDD) polychlorinated dibenzofuran (PCDF) and polychlorinated dibenzodioxins (PCDDs)

It is most appropriate to start with a discussion on PCBs, as they are the most understood of the endocrine-disrupting compounds (EDC) known. PCBs first began being produced in the 1930s, peaking in production in the 1970s, as heat exchange and dielectric fluids because of their significant insulating and non-inflammable properties (Auresenia et al, 2005). Furthermore, the term “dioxins” is used to refer to a group of PCB cousin compounds, such as polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF). Commercial PCB products used in industry were also a mixture of PCB forms, called congeners, with minute quantities of polychlorinated dibenzodioxins (PCDDs) contaminating the samples. A total of 1.25 billion pounds of PCBs were produced in the U.S. between 1930 and 1977, of which it is believed that 450 million pounds of PCB have entered our environment (Gehle et al, 2000). When indications of PCBs harmful effects to humans were seen and their ability to accumulate in the environment at vast quantities recognized, numerous countries began banning their use. This began with Sweden (1970), Japan (1972) and lastly the USA (1976) (Auresenia et al, 2005). PCBs are resistant to degradation and can therefore remain in the soil and bodies of waters for many years and can be easily passed up the food chain due to their lipophilic nature, residing in animal fat (Yang et al, 2006).

PCBs and Environment Contamination

Subsequent to the industrial explosion of PCB use, PCBs were being found in the environment secondary to poorly maintained waste dumps and landfills, illegal or improper dumping and disposing of hydraulic fluids and coolants, in addition to being dispersed as an aerosol (Marugh et al, 1975). High concentrations were being detected in numerous forms of life. This included entire food chains, such as seawater, plankton, small fish, bigger fish and fish eating animals, such as humans. Moreover, fish, beef, eggs, cheese, and other fat-containing foods were shown to contain high levels of PCBs (Assmuth et al, 2001). Depending on the consumption of fish, which is the main reservoir for PCBs that pass into humans, PCB concentrations in humans also vary, with people in Finland, the Far East, and other countries where fish forms a large component of their diet, being at the top of the list. In addition to fish and one’s diet, PCBs can enter the human system through contact and consumption of contaminated water, soil through skin absorption, and workplace environments through inhalation and contact.

References:

Auresenia J., Borja J., Gallardo S., and Taleon DM. 2005. Polychlorinated biphenyls and their biodegradation. Process Biochemistry. 40:1999-2013.

Gehle K., Johnson D., Pharagoodwade F., and Rosales-Guevara L. 2000. Case Studies in Environmental Medicine, Polychlorinated Biphenyl (PCB) Toxicity. ATSDR (Agency for Toxic Substances and Disease Registry). ASTDR-HE-CS-2003-0001.

Yang M, Park MS, and Lee HS. 2006. Endocrine Disrupting Chemicals: Human Exposure and Health Risks. J. Environmental Science and Health Part C. 24: 183-224.

Marugh II., and Thomas H. 1975. Chemical Pollutants: Polychlorinated Biphenyls Still a Threat. 190(4220):1189.

Assmuth T., and Louekari K. 2001. Research for management of environmental risks from endocrine disrupters. The Finnish Environment 448. Helsinki: Finnish Environment Institute.