Endocrine Disrupting Chemicals; A Risk to Human Health

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Endocrine Disrupting Chemicals or Endocrine Disruptors (EDCs) are environmental chemicals (natural or man-made) which directly or indirectly interfere with or mimic the endocrine (or hormone system). These substances "interfere with the synthesis, secretion, transport, binding, action, or elimination of natural hormones in the body that are responsible for development, behavior, fertility, and maintenance of homeostasis (normal cell metabolism)

Interference of normal human activities by these chemicals are associated with neurological, biological and mental disorders

• Immune suppression 
• Allergies
• Burns
• Childhood deformities
• Cancers
• Diabetes
• Poisoning        

Sources of Endocrine disrupting chemicals

They are found in many everyday products

• Insecticides, herbicides, pesticides, fumigants, fungicides used in agriculture and at home
• Synthetic and Naturally occurring hormones
• Personal care products: toys, cosmetics plastic bottles, detergents
•  Food and food products and additives
• Pharmaceutical drugs
• Industrial Chemicals
• Metals 

Examples of Endocrine Disrupting Chemicals

• Insecticides; DDT, Parathion, Pyrethroide, Diedrin, Carbaryl, Chlordan etc
•  Herbicides; Alachlor, Amitrol, Atrazin, 2, 4-Dichlorphenoxy-acetic acid, Metribuzin, Nitrofen, 2, 4, 5-Trichlorphenoxy-acetid acid.
• Nematicides; Aldicar, DBCP (1.2-Dibrom -3- chloropropan) 
•  Fungicides; Tributyltin compounds (TBT), Triphenyltin compounds (TBT), Maneb etc.
• Industrial chemicals; Alkylphenols, Bisphenol A, Dioxine (2, 3, 7, 8-TCDD), Pentachlorphenol, Phthalate, Polybromated Biphenyls (PBB), Polychlorinated Biphenyls (PCB), Polyethylene terephthalate (PET).
• Synthetic and Naturally occurring Hormones; Diethylstilbestrol (DES) 
•  Pharmaceutical drugs; Estradiol 
• Metal; lead and Mercury

Routes of exposure of Endocrine Disrupting chemicals in the environment

•   Contaminated food 
•   Water (Ground and surface water) 
• Air (Gas emissions from industrial sources)
• Contaminants in personal Care products and other consumer products

Mode of action of endocrine disrupting chemicals.

Endocrine Disrupting Chemicals can act: 

Directly
By binding to the receptors as:
a) Agonists - acting like natural hormones (E.g. ethinylestradiol, Nonylphenol)
b) Antagonists - blocking receptors for natural hormones (E.g. tamoxifen, TCB-77, DDT)

Indirectly by
 a) Influencing biosynthesis, metabolism, elimination and/or Bioavailability of natural hormones
 b) Inhibition of enzymes such as aromatase - blocking the transformation of androgens to estrogens

MAJOR EXAMPLES OF EFFECTS OF ENDOCRINE DISRUPTING CHEMICALS ON LIVING THINGS IN THE ENVIRONMENT

In Humans –    Reproductive effects such as decline in sperm quality, fertility, sex ratio effects and abnormalities of male sex organ, Nervous system function ,Immune function, Cancer (Breast cancer, Endometrial cancer, Testicular cancer , Prostate Cancer , Thyroid Cancer)
Fishes - Reproduction and development effects
Birds - Birth defects and egg shell thinning
Reptiles - Varieties in sex organ and other developmental abnormalities
Amphibians - Declines in their population
invertebrates -  Decline in their population and sex defects such as masculinization effects.

EDCs and Infectious Diseases

Low or high levels of exposures to such chemicals have varying degrees of adverse effects on the secretions and activities of hormones. Such disruptions are capable of influencing the development of infectious diseases and disease resistance because when EDCs interfere with endocrine balance, they disturb human immune functions                

This makes people vulnerable to infectious diseases they might otherwise have been able to resist be it TB, HIV/AIDS, malaria or other tropical diseases            

RECOMMENDATIONS

•  Read Certificate of analysis before any chemical/product is used
• Education: People have a right to know which chemicals may be endocrine disruptors and how they might be expose
• Detecting Exposures
• Environmental and human body cleanup  
• Laboratory testing (screening)
• Legislative measures

CONCLUSION

• This review provides information on Endocrine disrupting chemicals in the Nigerian environment and the world at large; types, sources, risk factors, those at risk, health implications and an insight into the control of exposure and management.
• There is a need to create awareness to the general public on the effects of EDCs in order to promote better environment and good health for wildlife and humans living in Africa.

AGU, REUBEN CHINEDU
Dept. of Biotechnology
FUTO, Nigeria