Monday, March 26, 2012
Is Our Drinking Water Safe?
The short answer is it depends on where your water comes from, and how it is treated. The drinking water supply can be broken down into three parts: the source water, the drinking water treatment system, and the distribution system which carries the treated water to homes and other buildings. The first steps towards a clean water supply and public health was to disinfect drinking water in the cities (and develop sewer systems). Treating drinking water with either Chloramine or chlorine lowered microbial densities of coliform bacteria, heterotrophic bacteria, Legionella bacteria preventing disease and death. However, these bacteria and the other substances on the primary drinking water list are not the whole story, nor are they the only substances in our water today. Our modern world is filled with chemicals, they exist in pharmaceuticals, household products, personal care products, plastics, pesticides, industrial chemicals, human and animal waste; they are in short, all around us. According to the Toxic Substances Control Act (TSCA) inventory of chemicals there are more than 84,000 chemical substances, as defined in TSCA today (or the last time they updated it). These chemicals include organics, inorganic, polymers, and UVCBs (chemical substances of Unknown or Variable composition, Complex reaction products, and Biological materials).
Public drinking water supplies are still typically treated with either Chloramine or chlorine both are disinfectants. (Disinfection by products are tested for in drinking water supplies.) Chloramine is a combination of chlorine and ammonia that is currently considered best technology for controlling the formation of certain regulated organic disinfection byproducts and has come to replace the use of chlorine in many locations. Since the revisions to the clean water act in the 1990’s chloramine has returned to common use as a distribution system disinfectant after being replaced in 1940’s with chlorine when there were ammonia shortages. Chloramine lowers microbial densities of coliform bacteria, heterotrophic bacteria, Legionella bacteria in the source water and distribution system while minimizing the formation of regulated disinfection by-products.
Under the authority of the Safe Drinking Water Act (SDWA), EPA sets standards for approximately 90 contaminants in drinking water including bacteria from human waste, industrial discharge streams (of great concern back in 1974 when the SDWA was first created) and water disinfection by-products and distribution system contaminants. For each of these contaminants, EPA sets a legal limit, called a maximum contaminant level. EPA requires that all public water supplies be tested for this list of contaminants on a regular basis (from daily, to quarterly, to every other year or longer depending on the contaminant and water system) and meet these minimum standards on average. In addition, EPA sets secondary standards for less hazardous substances based on aesthetic characteristics of taste, smell and appearance, which public water systems and states can choose to adopt or not. Though 90 contaminants is a lot, it is just a small fraction of the chemicals in large scale commercial production in the United States which EPA estimates to be over 7,000 chemicals.
Several of the substance controlled under the SDWA are natural occurring contaminants, 6 are bacteria and 8 are by-products or additives of water treatment; however, the greatest problem is pollution caused by mankind. Anthropogenic pollutants contaminate surface and groundwater as a result of manufacturing, combustion and incinerations air emissions, landfills and spills, stormwater runoff carrying agricultural and surface pollutants and waste water treatment water carrying a wide range of chemical containing substances into surface water and groundwater. The SDWA is a product of its time, in 1974 industrial waste discharge and release was far more common, and the last significant review of the SDWA was 1991. Six of the chemicals regulated under the SDWA have been banned for more than 20 years, but the US Geological Survey (USGS) found traces of at least one banned pesticide in groundwater during the recent study of the quality of the nation’s ground water supply.
The USGS ground water testing found that 10 contaminants were detected at concentrations greater than human-health recommended levels in 1% of the groundwater. Of the ten contaminants, seven were from natural sources and three were man-made. The seven contaminants from natural sources included four geological trace elements (arsenic, manganese, strontium, and boron) and three radionuclides (radon, radium, and gross alpha-particle radioactivity). The three contaminants that exceeded MCLs that were from man-made sources were nitrate (a nutrient), dieldrin (an insecticide that has been banned by the US EPA), and perchloroethene (PCE). Naturally occurring elements, radionuclides and pesticide compounds were extensively found at extremely low concentrations (about 10% of any existing health standard). Trace levels of an herbicide (atrazine or simazine) or an herbicide degradate (deethylatrazine), and the solvents perchlorethene or trichloroethene were widely found in samples from shallow unconfined aquifers without a confining geological layer, though the deeper confined groundwater aquifers remained mostly free of man-made contamination.
In their study of surface water used for drinking water supplies the USGS found a diverse group of contaminants in the source water. The concentrations were low, but the contaminants were ubiquitous. This would indicate a variety of different sources and pathways for these contaminants to reach our drinking water supplies. The concentrations were low, (about 95% of the concentrations were less than one-part per billion); nonetheless, the most commonly detected contaminants in source water were generally detected in finished water at about the same frequency and concentration. Our drinking water treatment systems do not remove these contaminants. The USGS found that as the amount of urban and agri-lands increased within the water shed, the numbers of contaminants in the rivers also increased. Rivers receiving municipal and industrial discharge, as well as discharges from other point and non-point sources from stormwater runoff are impacted by man-made organic contaminants, most of which are unregulated. Only about 40 of the 260 substances the USGS tested for are regulated the rest are unregulated.
The safety of our drinking water system is predicated on the basic assumption of toxicology that “dose makes the poison.” This relationship between exposure and risk has been challenged in the study of endocrine disruptors. Now, there is growing concern for potential endocrine disruptors at extremely low levels. Endocrine disruptors are chemicals that can mimic, block, or otherwise alter animal hormone responses, sometimes affecting their reproduction, development, and behavior, this is actually, how some pest control treatments are designed to work on bugs. A diverse group of chemicals called endocrine disrupting chemicals (EDCs) come from a variety of sources. These chemical have vastly different molecular structures, and become of great concern when they are discovered to be human endocrine disruptors.
The US Fish and Wildlife Service (USFW) and US Geological Survey (USGS) studied the relationship between waste water treatment plants, agricultural chemicals, and the immune-suppressed and inter-sexed fish in the Potomac River (and other locations). Hormones were not detected in the samples, but analysis using yeast screening assays found estrogenic endocrine-disrupting chemicals throughout the sections of the rivers tested, yet their specific source has not yet been identified. The extremely low concentrations of chemicals that was almost undetectable caused significant biological and health impacts among the fish and amphibian populations. Though they cannot identify a single chemical or group of chemicals responsible, the USFW and USGS have embarked on further study to gain greater understanding of the implications of their findings to the earth’s ecosystem.
The structural diversity of potential endocrine disruptors is enormous and it is not known which of these substances might adversely affect living things in subtle ways. Testing for new chemicals is for gross and acute impact, subtle impact is very difficult to identify. The growing class of known endocrine disrupting chemicals can disturb a staggering range of hormonal processes. Like natural hormones, some EDCs bind directly with hormone receptors. The impostors can mimic or block hormone messages with the same, weaker, or stronger responses. Others are more subtle, they interfere with hormone maintenance to prevent or enhance hormones from being made, broken apart, or carried in the bloodstream.
Recycled or reclaimed water is former wastewater (sewage) that has been treated to remove solids, bacteria and certain impurities, and then is used in irrigation, discharged to surface water that is a source of drinking water or injected into the ground to recharge groundwater aquifers. In order to make our river, lake, stream and ocean water safe for fishing and recreation, the Clean Water Act of 1972 mandated elimination of the discharge of untreated waste from municipal and industrial sources. This was the first great success of environmental regulations. Modern waste water treatment plants, usually using sand filtration and chlorination in addition to primary and secondary treatment, were required to meet certain standards. These standards were never designed to render the waste water potable nor to remove the vast number of chemicals and drugs that find their way down our drains today. The design of the combined sewer systems in the largest cities results in regular discharge of raw sewage during storm events. In the United States the cryptosporidium parasite has caused outbreaks of diarrheal disease in the 1990’s and boil water alerts are frequent occurrences in the in the 21st century. We are having difficulties maintaining our most basic water quality let alone protect the population from emerging contaminants. The Environmental Working Group has called for the EPA to do a national assessment of drinking water quality and establish new safety standards, set priorities for pollution prevention projects, and inform the public of the full range of pollutants in their water. In the meantime, while the EPA spends it time addressing carbon dioxide in the atmosphere you need to carefully consider source water quality, and treatment when selecting where to live.