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"People assume that if a product is on the shelves of their local store, it's safe," noted Dr. Susan Kegley, Senior Scientist at the Pesticide Action Network. "But 2,4-D is far from safe. When this herbicide is finally listed under Prop 65, the public will be notified that chemicals they are using on their lawn can affect women's ability to bear healthy children."
Currently, 2,4-D is widely used in neighborhoods. Forms of the chemical are found in approximately 660 agricultural and home use products in the United States. One popular use of 2,4-D is as a weed killer mixed with fertilizer for lawns, sold under brand names such as Trimec Weed and Feed™. Because companies mix herbicide and fertilizer in the same product, homeowners who simply want to fertilize their lawns often end up applying large doses of the herbicide as well. Approximately 46 million pounds of 2,4-D are used in the U.S. each year. Studies from the Centers for Disease Control indicate that fully one quarter of the U.S. population carries 2,4-D in their bodies, and children between the ages of six and eleven have significantly higher exposure rates compared to older children and adults.
The announcement represents important progress for state officials and public health advocates concerned about 2,4-D. OEHHA based its findings on the U.S. EPA's final Re-registration Eligibility Decision (RED) document, released in January 2005. EPA's analysis indicates that rats exposed to 2,4-D in utero showed an increased incidence of skeletal abnormalities such as extra ribs and malformed ribcages. In rabbits, 2,4-D and its diethanolamine salt caused abortions and skeletal abnormalities. The RED also indicated concerns about developmental neurotoxicity and endocrine disruption as possible toxicological outcomes for 2,4-D and related chemicals. EPA is requiring registrants to submit studies to assess the extent of these types of toxicity as a condition of re-registration.
EPA risk assessments indicate that home lawn care products account for 96% of the risk associated with using this chemical for the most sensitive sub-population (women of childbearing age), and that anticipated doses are very close to the level of concern. Exposures to 2,4-D can also come from other sources, including food residues and drinking water. EPA did not evaluate inhalation as an intermediate-term exposure source because no inhalation studies were submitted by the registrants, but noted this as a data gap that registrants must fill as a condition of re-registation. EPA also did not assess cumulative risk from exposures to multiple compounds similar to 2,4-D, which suggests that exposures might exceed EPA's level of concern with present use patterns if these additional exposures were taken into account.
Exposure to 2,4-D in drinking water is also coming under increasing scrutiny. U.S. EPA currently uses a limit of 70 parts per billion (ppb) as the level of concern, but the Minnesota Department of Health is proposing a draft guideline of six ppb for 2,4-D, based on EPA's own risk assessment. 2,4-D is capable of leaching into ground water, is sometimes used as an aquatic herbicide, and is used near waterways that may be drinking water sources.
The active ingredient 2,4-D and its derivatives were first marketed in 1944. These compounds have been off-patent for many years and are currently manufactured by many different companies around the world, including Dow Chemical, Agrolinz, Atanor, AH Marks (UK), Nufarm (Australia), Polikemia, Rhone-Poulenc, Sanachem, Sinochem (China) and Ufa, together with four other producers, in Turkey. The global market is estimated to be over US$300 million.
The 2,4-D family of chemicals are chlorophenoxy acids or esters, and are often used in mixtures with other chlorophenoxy compounds such as MCPA, MCPP, 2,4-DP and dicamba. These products are used as broadleaf herbicides in both terrestrial and aquatic applications, as well as plant growth regulators in citrus crops. Lawns, pastureland, wheat, corn and other cereal crops, as well as soy, sugarcane and forest land comprise the primary uses of 2,4-D. Approximately thirty million pounds (66%) are used by agriculture and sixteen million pounds (34%) in non-agricultural applications. Agricultural use in the U.S. is predominantly in the Midwest, Great Plains, and the Northwestern U.S.
OEHHA initiated the listing process for 2,4-D through the Authoritative Bodies mechanism, in which the state of California uses documentation produced by another agency with expertise and authority in assessing toxicity. On December 15, 2005, the agency extended the comment period to February 2, 2006 for submission of comments on the proposed listing. Instructions for submitting comments can be found at the OEHHA web page announcing the Notice of Intent to List.
Reproductive and Cancer Hazard Assessment Branch, Office of Environmental Health Hazard Assessment, California Environmental Protection Agency. 2005. "Chemicals Meeting The Criteria For Listing Via The Authoritative Bodies Mechanism: (2,4- Dichlorophenoxy) Acetic Acid (2,4-D), 2,4-D N-Butyl Ester, 2,4-D Isopropyl Ester, 2,4-D Isooctyl Ester, 2,4-D Propylene Glycol Butyl Ether Ester (2,4-D Pgbe), 2,4-D Butoxyethanol Ester And 2,4-D Dimethylamine Salt". [http://www.oehha.ca.gov/prop65/CRNR_notices/admin_listing/intent_to_list/extendpkg5d.html]
U.S. Environmental Protection Agency. 2005. "Reregistration Eligibility Decision for 2,4-D. Office of Prevention, Pesticides and Toxic Substances". [http://www.epa.gov/oppsrrd1/REDs/24d_red.pdf]
Pesticide Action Network United Kingdom. 1997. "2,4-D Fact Sheet". [http://www.pan-uk.org/pestnews/Actives/24d.htm]
Minnesota Department of Health. Draft Health Risk Limits for Groundwater, [http://184.108.40.206/divs/eh/groundwater/hrlgw/draftsonar.pdf]