The endocrine system found in all mammals, birds and fish is made up of glands, hormones and receptors in various organs, and is the system that regulates all hormonal activity in animals. Disruption of the endocrine system can occur in several ways. Some chemicals can mimic a natural hormone, causing the body to over react to the hormone or responding at inappropriate times. Endocrine disrupting chemicals can block the effects of a hormone or can directly stimulate or inhibit the endocrine system, causing overproduction or underproduction of hormones. Certain drugs are used to intentionally cause some of these effects, such as birth control pills. However, in many situations involving environmental chemicals, an endocrine effect can disrupt the proper functioning and development of the animal.
In recent years, it has been proposed that some trace, environmentally persistent chemicals might be disrupting the endocrine systems of humans and wildlife. A variety of chemicals have been found to disrupt the endocrine systems of animals in laboratory studies, and compelling evidence shows that endocrine systems of certain fish and wildlife have been effected by chemical contaminants, resulting in developmental and reproductive problems (Blazer et al, 2004). However, the relationship of human diseases of the endocrine system and exposure to environmental contaminants is poorly understood and still scientifically controversial.
Recently, concern has emerged about a group of trace organic compounds identified in the aquatic environment which might affect reproduction and development of wildlife species and humans due to endocrine disruption. EDCs are a structurally diverse group that includes natural and synthetic estrogens, alkyl phenols surfactants, phthalates, bisphenol A, brominated flame retardants and some pesticides. Studies in recent years have documented a wide occurrence of endocrine disrupting compounds (EDCs) in aquatic ecosystems not solely associated with waste water treatment plants. This could indicate non-point sources of contamination, which may have serious implications for groundwater quality. The use of groundwater has been increasing not only for private wells and agriculture but also for municipal supply. USGS hydrologists believe that the potential for EDC contaminated surface water and run off to impact groundwater has increased. A second area of concern is for EDCs to impact groundwater through the leaching of septic system effluents. Septic systems are utilized at 25-30% of all households. Non-sewer subdivisions which represent a fairly high density use of septic may have an increased susceptibility to contamination of the groundwater by EDCs. Suspect EDCs are used in large quantities by consumers and industry. Domestic and industrial wastewater and agricultural run-off are recognized as the major sources of EDCs.
During the late 1990’s in research performed by several studies identified EDCs not only in wastewater effluents, but also at low concentrations in surface and groundwater in use for drinking water supply, and at very low concentrations in tap water samples. In a study performed in 2004-2006 at the University of Wisconsin using EDC estrogenic activity as a test for EDC activity found all surface waters tested contained some levels of estrogenic EDC activity. Water from high capacity groundwater wells did not contain any measurable estrogenic EDC activity. Estrogenic activity was detected in 20 of 21 septic effluent samples, although concentrations were markedly reduced in systems utilizing either sand filtration or aerobic pretreatment as compared to traditional systems. In general, concentrations in conventional systems were comparable to those measured in previous studies of municipal wastewater treatment plant (WWTP) influent, and concentrations in systems after advanced treatment were comparable to previously measured concentrations in WWTP effluent. The data indicates that septic systems using advanced treatment can reduce EDCs in treated effluent to similar concentrations as municipal WWTPs.
Although low levels of activity was detected in soil water directly beneath one septic system, no estrogenic activity was found in groundwater in this study. There appears to be no infiltration of estrogenic endocrine disrupting chemicals from the surface waters into the associated ground waters. Advanced pretreatment technologies (aerobic, sand filtration) appear to be quite effective at removing estrogenic compounds from septic effluent. Additional removal of EDCs occurs in unsaturated soils beneath septic leach fields; no EDCs were detected in groundwater beneath the systems without advanced pretreatment.
No comments:
Post a Comment