Daily News Archives
Finds Pesticides In Nation's Surface and Ground Water
(Beyond Pesticides, May 26, 2004) In
agricultural and urban areas, the quality of our nation's water resources
has been degraded by contaminants such as pesticides, nutrients, and
gasoline-related compounds, according to Water
Quality in the Nation's Streams and Aquifers-Overview of Selected Findings,
1991-2001 released earlier this month. Based on a series of
51 United States Geological Survey (USGS) reports on the health of major
river basins across the country (15 of which were also released earlier
this month), the overview states that insecticides such as diazinon
and malathion were found in nearly all of the streams that were sampled
in urban areas. Streams in agricultural areas were more likely to contain
herbicides-especially atrazine, metolachlor, alachlor, and cyanazine.
For more than a
decade, USGS hydrologists have looked at three questions related to
ground and surface water quality. What are the conditions of our nation's
streams and ground water? How is water quality changing over time? And
how do natural features and human activities affect the quality of streams?
According to the USGS Chief Hydrologist Robert Hirsch, "By evaluating
and assessing our nation's water resources, we have a better understanding
of water quality and this gives us a comprehensive picture of the long-term
health of America's rivers and aquifers. We have analyzed the effects
of agricultural, urban, and forest land use practices on water quality,
habitat, and biota."
Some specific findings
regarding pesticides are highlighted below.
Ohio and southeastern Indiana:
- Atrazine and
metolachlor, herbicides that are heavily used on agricultural land,
were detected in more than 90% of samples from 5 streams in southwestern
Ohio, whereas insecticides (such as diazinon) commonly used by homeowners
were frequently detected in an urban stream.
- In 29 small stream
basins that drain areas of various land uses, USGS scientists found
that insecticide concentrations increased as the amount of urban land
biphenyls (PCBs) and organochlorine insecticides, such as DDT and
chlordane, continue to persist in fish tissue even though their use
was canceled or restricted in the 1970s and 1980s. Many of these chemicals
were detected at concentrations at or near the maximum concentrations
found nationwide by the NAWQA Program.
- Very low concentrations
of one or more pesticides were detected in 63% of the groundwater
samples from 96 wells. (None of the concentrations exceeded drinking-water
standards or guidelines.)
Karst Areas in
the Lower Tennessee River Basin:
- Fifty-two pesticides
(38 herbicides, 11 insecticides, and 3 fungicides) were detected in
streams and rivers. (Aquatic-life guidelines were exceeded in less
than 3% of the samples.)
- Although uses
of DDT and PCBs were discontinued more than 20 years ago, residues
of these compounds continue to be detected in fish tissue throughout
the Basin. (Less than 3% of the sites had concentrations that exceeded
human health action levels or wildlife guidelines.)
- Although 35 pesticides
were detected in wells and springs sampled in carbonate aquifers,
none of the detected pesticides exceeded the USEPA drinking-water
standards. Pesticides detected in the ground water reflect differences
in land uses. General-use pesticides that are applied along road and
power line rights-of-way and in urban areas to control woody vegetation
and weeds were detected at similar frequencies in the two carbonate
aquifers sampled. Cotton, corn, and soybean production is concentrated
in the rolling terraces and floodplains of the Eastern Highland Rim.
The underlying aquifer in these areas had higher detection frequencies
of agricultural pesticides than areas where pasture land is more prevalent.
- VOCs and pesticides
were detected together in more than half of sampled public-supply
wells, with one exception.
- Of some 80 similar
USGS studies, Oahu ranked first in the nation in the percentage of
wells in which fumigants were detected. Fumigants have long been applied
to pineapple fields to combat nematodes (rootworms).
- Four wells exceeded
state standards for the fumigants DBCP and TCP. (Where standards were
exceeded, the wells already had been taken out of service or were
receiving treatment to remove the contaminants.)
- Several chemicals
in stream water and bottom sediment exceeded guidelines established
to protect the health of stream animals and fish-eating wildlife.
Sediment concentrations of the pesticides dieldrin, chlordane, and
DDT were in the highest 5% of streams sampled nationally by USGS,
and similarly high concentrations were present in fish tissue. Dieldrin
and chlordane were highest in urban areas where they were used to
kill termites, and DDT was highest where it had been used for agriculture.
Hirsch noted that,
"Concentrations of contaminants in water samples from wells were
almost always lower than current EPA drinking-water standards and guidelines.
However, the possible risk to people and to aquatic life can only be
partially addressed because of the lack of criteria for many chemicals
and their degradation or "breakdown" products. In addition,
criteria were developed for individual chemicals and do not take into
account exposure to mixtures or seasonal high pulses in concentrations."
The 51 reports on
water quality were conducted since 1991 by the USGS
National Water Quality Assessment (NAWQA) program. Of the 51 areas
studied in the first phase of the program, the USGS has already launched
a second round of studies in 42 areas to determine trends, fill critical
gaps in the characterization of water-quality conditions, and increase
understanding of natural and human factors that affect water quality.
Help protect our nation's water by creating a healthy, pest-resistant
lawn without the use of toxic pesticides. Find out how here.
Get rid of other pests without hazardous pesticides by going to Beyond
Fact Sheets. You can also join the Pesticide-Free
Zone Campaign and national network.