Published online Jan 8. Schmehl2 Christopher A. Mullin1 and James L. The authors have declared that no competing interests exist.
Although nitrate and bacterial contamination were known to occur in some locations, groundwater was thought to be immune from more serious forms of pollution such as industrial discharges, hazardous waste dumps, or leaching of pesticides from agricultural operations.
Synthetic organic compounds are chemicals synthesized from carbon and other elements such as hydrogen, nitrogen, or chlorine. They do not occur naturally, but are manufactured to meet hundreds of needs in our daily lives, ranging from moth balls to hair sprays, from solvents to pesticides.
Why have they only recently been discovered in groundwater? One reason is that use of synthetic organic compounds has greatly increased within the past 40 years, and some of these gradually have made their way into groundwater.
Another reason for the recent discoveries of organic contaminants in groundwater is that the laboratory capability to detect these chemicals has greatly improved within the past decade. A classic example of this occurred in Bedford, Massachusetts, where severe organic chemical contamination of the town groundwater supply was discovered in only because a resident engineer took a sample of his home tap water with him to work where he was developing and testing a new laboratory instrument for analyzing organic chemicals.
The Bedford contamination eventually was traced to several local industries that were improperly disposing of their chemical wastes. Now that people are aware of organic contaminants in drinking water, sampling for such chemicals has increased, and more than synthetic organic compounds have been identified in various U.
This contamination originates from a variety of sources, including household products and leakage or improper disposal of chemical wastes from commercial and industrial establishments. By-products of industrial manufacturing or cleaning operations have been disposed of in unrecorded dump sites across the nation, and some of these chemicals have leached to groundwater.
Pesticides constitute another, smaller category of synthetic organic compounds, some of which have been found in groundwater. Between and production of synthetic organic pesticides more than tripled in the United States, from about million pounds in to over 1.
Although most of these compounds have not been detected in groundwater, a few have become significant contaminants. Twenty- two pesticides have been detected in U. One area with conditions highly conducive to leaching is Long Island, New York, where soils are sandy, the water table is shallow, and agriculture is intensive.
A total of 13 pesticides have been detected at least once in Long Island groundwater, and 8 of these have been found multiple times through continued monitoring. In upstate New York, sampling for pesticides has been limited to measurement of aldicarb in wells near treated fields.
Low concentrations of aldicarb have been detected in 30 percent of the 76 wells sampled. Twenty-two other states, including Maine, Maryland, and New Jersey, also have reported some pesticide contamination of groundwater.
This bulletin focuses on the health effects of pesticides in drinking water, although the same concepts also apply to the much wider range of synthetic organic compounds contaminating groundwater supplies.
Types of Pesticides in Groundwater The health effects of pesticides depend upon their chemical characteristics. Before the s most pesticides were compounds of arsenic, mercury, copper, or lead. Although these compounds may have made their way into drinking water, they were not highly soluble, and the residues ingested in foods were of far greater concern.
Synthetic organic pesticides were introduced during World War II and were thought to be far safer and more effective. These included chlorinated hydrocarbons such as DDT, aldrin, dieldrin, chlordane, heptachlor, lindane, endrin, and toxaphene. Because of their low solubility in water and their strong tendency to chemically attach to soil particles, these compounds have rarely contaminated groundwater.
They originally were thought to be safe to humans and the environment, but later were discovered to accumulate in the environment and build up to toxic concentrations in food chains.
Use of most of the chlorinated hydrocarbon pesticides, consequently, has been restricted, suspended, or canceled. One group replacing them has been the organophosphorous compounds such as malathion and diazinon. Although some organophosphorous compounds are highly toxic to humans, they generally break down rapidly in the environment and rarely have been found in groundwater.
Another group replacing the chlorinated hydrocarbons are carbamate pesticides including aldicarb, carbofuran, and oxamyl.
These compounds tend to be soluble in water and weakly adsorbed to soil. Consequently, if not degraded in the upper soil layers, they have a tendency to migrate to groundwater. The most significant occurrences of groundwater contamination have been with the carbamate pesticides.
Aldicarb has been detected in over 2, wells on Long Island as well as in 12 other states including Maine and New Jersey. As awareness has grown of the potential for pesticides to leach to groundwater, attention has focused on ways of changing registration and monitoring requirements to prevent such contamination from occurring in the future.
Intensive studies have also been carried out in an attempt to determine what levels of pesticides are acceptable in water supplies.
Health Effects of Pesticides Studies of the health effects of pesticides on humans focus on two aspects, the acute toxicity, or immediate effects resulting from short-term exposure, and the chronic toxicity, or effects resulting from more-prolonged exposures.
Acute toxicity typically is expressed as the concentration required to kill 50 percent of a population of test animals such as laboratory rats, either through ingestion or through contact with the skin. These lethal concentrations can vary greatly from one pesticide to another.Jan 08, · Unfortunately, despite the potential toxicity of ‘inert’ ingredients and their widespread use in pesticide products, their testing and risk assessment seems to be inadequate.
Synergy: The Big Unknowns of Pesticide Exposure Daily combinations of pesticides and pharmaceuticals untested their property to reduce mosquito effect in dogs for the acute toxicity of EPN and malathion administered simultaneously.
Pesticide authorization in the EU—environment unprotected? Sebastian Stehle 1 & Ralf Schulz1 out of various organic pollutants, insecticides particularly jeopardize the integrity of EU freshwater ecosys-tems.
In addition, several additional small-scale field studies Table 1 The insecticides included in the meta-analysis, their final. Synthetic Pyrethroids: Toxicity and Biodegradation. A.J. Thatheyus Chronic sequelae to pyrethroids exposure include cerebro-organic disorders, Though they are said to have rapid rate of degradation in the environment, their adsorption to sediments increases their persistence by rendering them unavailable to SP-degraders which are.
Cypermethrin Residues in Fresh Vegetables: Detection by HPLC and LC-ESIMS and their Effect on Antioxidant Activity M. Debbab1, S. El Hajjaji2*, Amal H. Aly3, A. Dahchour4, Although the naturally occurring pyrethrins are effective insecticides, their.
New and innovative pesticides are being developed and are applied in the environment every year. In many cases, methods to assess the fate of these new pesticides and their degradates in .