Toxicants are poisonous substances that are produced artificially and introduced to the environment as a result of human activities. These toxicants have serious implications on human health. For instance, they have been found to affect vital organs of the body and lead to death in some cases.
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PCBs (Polychlorinated Biphenyls) are among the most dangerous persistent organic toxicants in the environment that have been known to adversely affect the health of humans, animals, and the environment. This article focuses on the effects of PCBs on the respiratory system, the immune system, and the liver.
A toxicant is a xenobiotic substance that produces hazardous effects on the body or the environment. Toxicants are introduced into the environment through as a result of human activities. Most of these toxicants mostly circulate through the body and accumulate in specific target organs, which they eventually affect adversely.
However, others can damage any cell or tissue that they come into contact with. There are numerous toxicants in the environment, including heavy metals, non-metals, radioactive pollutants, and persistent organic pollutants (Kacew & Lee, 2013).
Polychlorinated Biphenyls (PCB) toxicants are classified under persistent organic pollutants. They are artificial organic chemicals with a slow breakdown, thus they remain for long in the body system or the environment. A variety of health effects can occur in particular body organs and systems when the human body system is exposed to PCBs.
PCBs can lead to immunotoxicity, either in the form of hypersensitivity like in allergy, as well as autoimmune, immunodeficiency, and uncontrolled growth. Studies have found out that PCBs impair the immune system function. They bind to receptors that are responsible for immune system function control, resulting in disturbances in lymphocytes and T cells.
A study conducted on Dutch children found a remarkable reduction in the immune system function associated with PCBs’ exposure (Weisglas-Kuperus et al., 2000). Studies in the rhesus monkey revealed that exposure to PCBs can bring about reduction of the thymus, slowed immune response, and reduced Epstein –Barr Virus resistance, as well as other infections (Kacew & Lee, 2013).
PCBs also affect the liver adversely. This was recognized as early as the 1930s. PCBs have been associated with the production of abnormal enzymes of the liver and suspected non-alcoholic fatty liver disease (NAFLD) (Shi et al., 2012).
They induce microsomal enzymes, particularly EROD (this is the marker for CYP1A1) and urinidine diphosphate glucuronyl transferase (UDPGT), which in turn lead to hepatogenic porphyria, as well as high endogenous steroid degradation in the liver. Induction of CYP1A1 has been said to promote cancer and hyperplasia sensitivity, as well as necrosis and fatty infiltration (Kacew & Lee, 2013).
Exposure to PCBs also poses adverse effects on the respiratory system. The enzymes uridine diphosphate glucuronyltransferases (UDPGTs) produced in the liver as a result of PCB exposure can also be induced in the lungs, among other body organs. This has the same effect with the effect in the liver; that is, cancer (Kacew & Lee, 2013).
Structural damage can occur in the lungs if exposed to PCB toxicants for long, leading to chronic diseases like pulmonary fibrosis, emphysema, besides cancer. Chronic exposure to PCBs via inhalation has been found to lead to symptoms in the respiratory tract, like cough and chest tightness. Exposure to PCBs also increases the vulnerability to asthma, as well as other infectious respiratory diseases (Carpenter, Ma & Lessner, 2008).
Carpenter, D. O., Ma, J., & Lessner, L. (2008). Asthma and infectious respiratory disease in relation to residence near hazardous waste sites. Ann N Y Acad Sci. 1140, 201-208. doi: 10.1196/annals.1454.000.
Kacew, S., & Lee, B. M. (2013). Lu’s basic toxicology: Fundamentals, target organs, and risk assessment (6th ed.). New York, NY: Informa Healthcare.
Shi, X. et al. (2012). Metabolomic analysis of the effects of polychlorinated biphenyls in non-alcoholic fatty liver disease. Journal of Proteome Research, 11(7), 3805-3815. doi: 10.1021/pr300297z.
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Weisglas-Kuperus, N., Patandin, S., Berbers, G. A., Sas, T. C., Mulder, P. G., Sauer, P. J., & Hooijkaas, H. (2000). Immunologic effects of background exposure to polychlorinated biphenyls and dioxins in Dutch preschool children. Environmental Health Perspectives, 108(12): 1203-1207.