National Drinking Water Database
Methoxychlor in California
Methoxychlor is an endocrine-disrupting insecticide similar to DDT; banned in the U.S. in 2002, it was historically used on farm animals and in animal feed, lumber, gardens and certain crops. [read more]
Methoxychlor, an organochlorine insecticide and a chemical analog of a highly toxic pesticide DDT, has been used on animals, in animal feed, and on certain crops such as squash and melons (U.S. Environmental Protection Agency (USEPA) 2004b). The major source of methoxychlor in drinking water has been runoff and leaching from insecticide applied on cattle, lumber and gardens.
The use of methoxychlor in the U.S. was canceled by the EPA in 2002 due to significant concerns about the effects of methoxychlor on human health and the environment, including concerns about its endocrine disruption effects and persistent, bioaccumulative toxicity (USEPA 2004b).
As a class, organochlorine pesticides like methoxychlor are toxic, persistent, bioaccumulative, and lipophilic ("fat-loving"). Due to these properties, organochlorine pesticides build up and are stored in fatty tissues and fluids, such as breast milk, and can be passed on to fetuses and infants during pregnancy and lactation. Organochlorine pesticides cause significant neurotoxicity in laboratory animals and humans, which is not surprising since they were designed to attack the nervous system of insects. In addition, many organochlorine pesticides disrupt the hormone and the immune systems (Seth 2005; Tiemann 2008; Colt 2009).
Exposures to levels of methoxychlor in drinking water above the maximum contaminant level (MCL) of 40 parts per billion (ppb) may cause damage to the liver, kidney and heart, and reproductive difficulties (USEPA 2009b). In laboratory animals, methoxychlor causes neurotoxicity with symptoms such as tremors, convulsions and seizures (Lafuente 2007). Developmental and adult dietary exposure to methoxychlor also damages the immune system in laboratory animals (Agency for Toxic Substances and Disease Registry (ATSDR) 2009b).
Methoxychlor and its metabolites possess estrogenic, anti-estrogenic, and anti-androgenic activities and act as endocrine disruptors (Zama 2009). Exposure to methoxychlor has been shown to cause abnormalities of the ovaries and uterus, early puberty and altered reproductive cycles in females. In the male, methoxychlor cause testicular and prostate toxicity and decreased sperm counts. Decreased fertility is found in both males and females. Many of the reproductive effects of methoxychlor have been found following fetal or neonatal exposure (ATSDR 2002d).
The Most Polluted Communities in California
1 water utilities reported detecting Methoxychlor in tap water since 2004, according to EWG's analysis of water quality data supplied by state water agencies
Ranked by highest average Methoxychlor level
|Rank||System||Population Served||Positive test results of total reported tests||Average Level|
|1||Lost Hills Utility District|
Lost Hills, CA
|2,772||1 of 2||0.22 ppb|
(0 to 0.44 ppb)
Health Based Limits for Methoxychlor
|California Public Health Goals||Defined by the State of California Office of Environmental Health Hazard Assessment (OEHHA) as the level of contaminant that is allowed in drinking water. For acutely toxic substances, levels are set at which scientific evidence indicates that no known or anticipated adverse effects on health will occur, plus an adequate margin-of safety. PHGs for carcinogens or other substances which can cause chronic disease shall be based solely on health effects without regard to cost impacts and shall be set at levels which OEHHA has determined do not pose any significant risk to health.||30 ppb|
|Maximum Contaminant Limit (MCL)||The enforceable standard which defines the highest level of a contaminant that is allowed in drinking water. MCLs are set as close to health-based limits (Maximum Contaminant Level Goals, or MCLGs) as feasible using the best available analytical and treatment technologies and taking cost into consideration. Source: U.S. Environmental Protection Agency.||40 ppb|
|Maximum Contaminant Limit Goal (MCLG)||A non-enforceable health goal that is set at a level at which no known or anticipated adverse effect on the health of persons occurs and which allows an adequate margin of safety. Source: U.S. Environmental Protection Agency.||40 ppb|
|Lifetime health-based limit, non-cancer risk||Concentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic health effects for a lifetime of exposure. The Lifetime health-based limit (or Health Advisory, HA) is based on exposure for a a 70-kg adult consuming 2 liters of water per day. Source: U.S. Environmental Protection Agency.||40 ppb|
|Children's health-based limit for 1-day exposure||Concentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic health effects for up to one day of exposure. The One-Day health-based limit (or Health Advisory, HA) is typically set to protect a 10-kg child consuming 1 liter of water per day. Source: U.S. Environmental Protection Agency.||50 ppb|
|Children's health-based limit for 10-day exposure||Concentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic effects for up to ten days of exposure. The Ten-Day health-based limit (or Health Advisory, HA) is typically set to protect a 10-kg child consuming 1 liter of water per day. Source: U.S. Environmental Protection Agency.||50 ppb|
|EPA Human Health Water Quality Criteria||Water quality criteria set by the US EPA provide guidance for states and tribes authorized to establish water quality standards under the Clean Water Act (CWA) to protect human health. These are non-enforceable standards based upon exposure by both drinking water and the contribution of water contamination to other consumed foods. Source: U.S. Environmental Protection Agency.||100 ppb|
|Drinking Water Equivalent Level||A lifetime exposure concentration protective of adverse, noncarcinogenic health effects, that assumes all of the exposure to a contaminant is from drinking water. Source: U.S. Environmental Protection Agency.||200 ppb|
Violation Summary for Methoxychlor in California
Data from the U.S. Environmental Protection Agency includes the following violations of federal standards in California since 2004
|Violation Type||Number of Violations|
|Failure to monitor regularly||2|