Cancer-Causing Pesticide ‘Garbage’ Taints Tap Water for Millions in California

UPDATE: Since the publication of this report on April 11, 2017, additional analysis of water utility tests by EWG has shown 1,2,3-trichloropropane, or TCP, to be a contaminant in the drinking water of at least 21 states.

California produces two-thirds of America's fruits and nuts, and a third of its vegetables, with the lion's share grown in the 250-mile-long San Joaquin Valley. But the bounty comes with a price: widespread contamination of drinking water from agricultural chemicals.

Among the most toxic is 1,2,3-trichloropropane, or TCP, an extremely potent carcinogen that was formerly an impurity in the pesticides Telone, made by Dow, and D-D, made by Shell. Telone and D-D were fumigants – poisonous gases injected into the soil before planting crops, to kill microscopic worms called nematodes. Shell stopped making D-D in 1984 and Dow later took TCP out of Telone – but not before it contaminated the tap water supplies of millions of Valley residents.

TCP in drinking water is currently unregulated by both the state of California and the U.S. Environmental Protection Agency. California will soon set a legally permitted limit – a Maximum Contaminant Level, or MCL – requiring public utilities to test their water and, if needed, install filters to lower the level of the chemical. But according to lawsuits against Dow and Shell filed by dozens of San Joaquin Valley cities and towns, TCP – which a Dow scientist once described as “garbage” – was hazardous waste that never should have been in the pesticides in the first place.

“TCP was an unnecessary chemical byproduct that had no role in killing nematodes,” said Asha Kreiling, an analyst with the Community Water Center, a group that advocates for safe and affordable drinking water in the Valley and, with the California office of Clean Water Action, has worked to push for a legal limit of the carcinogen.

“Dow and Shell knew that – they knew it could pollute groundwater and they were fully aware of the health impacts,” Kreiling said. “They should have taken it out and disposed of it properly as a toxic waste. But that would have cost them a lot of money, so they left it in and continued to sell these pesticides to farmers throughout California."

"Shell and Dow put greed for profits ahead of the health of the people who bought and used their products," said Andria Ventura, toxics program manager for Clean Water Action. "We can't reverse the tragic consequences, but setting a drinking water standard that's fully protective of public health can stem the threat going forward.”

According to the State Water Resources Control Board, since 2001 TCP has been detected in water systems serving more than 8 million Californians. In 94 public water systems, TCP has been detected at levels higher than the board’s proposed legal limit. Of the 562 contaminated wells within those systems, about 60 percent are in the San Joaquin Valley, concentrated in Kern, Fresno and Tulare counties, the three leading agricultural counties in the state (see Table 1 below). And the list could grow longer.

Quote by Asha Kreiling with the Community Water Center

Todd Robins, a San Francisco attorney who represents 33 smaller Valley communities in their lawsuits, said the number of water supplies known to be contaminated will increase once a legal standard is set that requires utilities to test for TCP. California's proposed legal limit is important to the outcome of the lawsuits because "it confirms, as the plaintiffs have said all along, that detectable levels of TCP in drinking water are unacceptable based on cancer risk," he said.

“The cost of treatment should not be borne by residents of the impacted communities," Robins said. "Safe and affordable drinking water is a human right, and we are committed to see that every last well is treated, and that Dow and Shell are held responsible.”

Table showing TCP Detections in California Public Water Systems

In 2009, the California Office of Environmental Health Hazard Assessment, or OEHHA, set the extraordinarily low public health goal for TCP in tap water of less than one part per trillion – about 1,000 times smaller than a drop of water in an Olympic-size swimming pool.[1] That's a lower public health goal than the state has for any other chemical except dioxin, often described as the most toxic compound known to science.[2]

Public Health Goal in Context

A public health goal is based solely on scientific and public health concerns. It is not a legally enforceable limit, which takes into account the cost and feasibility of treatment, but a minimum risk level that would be expected to cause no more than one additional case of cancer in a million people who drink the water and shower with it daily for a lifetime.

OEHHA based the public health goal on a 1993 study by the National Toxicology Program, or NTP, that found TCP caused stomach, liver and other cancers in mice and rats.[3] The NTP classifies TCP as "reasonably anticipated" to cause cancer in people.[4] TCP is in California’s official registry of chemicals known to cause cancer,[5] and last year an OEHHA scientist told KQED-FM: "There is absolutely no question it is a genotoxic carcinogen."[6] The EPA says long-term TCP exposure is also linked to liver and kidney damage.[7]

There is no federal standard for TCP. But under an EPA testing program, between 2013 and 2015, it was detected in 13 states besides California, in drinking water supplies serving about 4 million people[8] (see Table 2 below). EPA's minimum required reporting level of 30 parts per trillion was six times higher than California’s, so the true extent of nationwide contamination is likely much greater.

Table showing drinking water suppies outside California contaminated with TCP

Hawaii, where D-D and Telone were heavily used on pineapples, is the only state with a legal limit for TCP in drinking water – 0.6 parts per billion, or 600 parts per trillion.[9] In October, a state scientific advisory panel in New Jersey, where TCP was used as an industrial solvent, recommended a limit of 30 parts per trillion, 20 times lower than Hawaii’s.[10]

In California, staff of the Water Resources Control Board have proposed an even stricter limit, 5 parts per trillion, which they say is the lowest level tests can reliably detect.[11] The water board says that level poses an increased lifetime cancer risk of about one in 143,000. A public hearing on the proposed limit, which is supported by Community Water Center, Clean Water Action, EWG and other groups, will be held April 19 in Sacramento.

“TCP has been detected all over California, but more than half of the state’s contaminated wells are found in the agriculturally rich San Joaquin Valley, particularly in Kern, Fresno, and Tulare counties,” the groups wrote last month to the water board. “[These] rural, lower-income regions, where residents are already threatened by disproportionate exposure to contaminated water and other pollution, often lack the adequate resources to address these problems or the associated medical consequences.” The groups say the proposed legal limit "would expedite cost-recovery efforts that have been pending for years, while providing strong health protection and limiting medical costs."

Quote by Todd Robins

The major source of TCP in California tap water was once thought to be toxic waste sites. In 1999, TCP was found leaching from federal Superfund cleanup sites in Southern California, where it was used as a solvent in aerospace plants. Contaminated drinking water sources in that area are being treated with money from federal grants and lawsuit settlements. State regulators subsequently ordered testing that found TCP in water supplies throughout the San Joaquin Valley and in some other farming areas.

Robins, the attorney representing smaller Valley communities, has spent a decade researching the chemical. He said TCP was first produced in the 1930s by Shell as one of dozens of unwanted byproducts from the process of making allyl chloride, a chemical used to manufacture plastics. Pineapple growers in Hawaii experimented with the mixture of byproducts and found it worked to kill nematodes.

Take Action to help get cancer-causing pesticides out of drinking water!

Shell, and later Dow, began marketing slightly different formulations of the mixture and eventually Telone and D-D became the second most heavily used pesticides in California. Their main and effective ingredient was 1,3-dichloropropene, or 1,3-D. Telone and D-D contained very small amounts of TCP, but the heavy use of these products spread hazardous levels of the chemical throughout the Valley.  

In lawsuits against Shell and Dow, Robins and other attorneys charge that as early as 1952 researchers knew TCP in fumigants did not break down in soil and posed a risk to groundwater.[12] Once it migrates into groundwater, TCP persists for centuries.[13] Robins said the major studies linking TCP to cancer were not done until the 1990s, but the health hazards of chlorinated pesticides were well-known decades earlier.  

Picture of Cecy Gonzales


Cecy Gonzalez, B​akersfield, Calif. who went to the state Capitol to urge the state to set a legal limit for TCP.

The lawsuits also charge that Shell and Dow knew TCP was useless as a pesticide – in fact, they made the fumigants less effective. But the product labels said Telone and D-D contained 100 percent active ingredients – false claims that violated federal regulations for registering pesticides.[14] In a 1949 internal communication, Shell said it preferred “not to list all the ingredients” in order to “retain the definite sales advantage of a 100 percent active ingredient claim.”[15]

Dow Chemical document

In 1974, a Dow scientist predicted tighter EPA rules would force the removal of TCP and other impurities, collectively known as chlorinated aliphatics, from Telone because the company could not show they had any value as pesticides. In a letter to a customer, the scientist wrote:

. . . EPA will not let us apply the amount of garbage . . . that is applied with the 1,3-D. I call it garbage because it is unlikely that anyone could justify the toxicology [nematode-killing ability] for the other numerous chlorinated aliphatics present.

The lawsuits charge that although scientists recommended removal of TCP and other impurities from D-D and Telone, Shell and Dow had strong financial motives for leaving them in. A 1983 Shell internal memo said that annual sales of D-D not only earned $6.3 million, but also netted "a savings of $3.2 [million] for cost avoidance for disposal in the allyl chloride operation."[16]

Dow and Shell deny any wrongdoing. In court documents the companies say, among other arguments, that they are not liable for TCP contamination because their use of Telone and D-D was legally authorized by the EPA and the California Department of Pesticide Regulation.[17][18] However, without admitting guilt, the companies have paid multi-million dollar settlements to some Valley cities.

The amounts of legal settlements are often confidential. But in one recent case that went to trial and reached a verdict, Shell was ordered to pay $22 million to Clovis, a suburb of Fresno, in December. Clovis, with a population of about 100,000, previously settled with Dow for a reported $7.5 million.[19] The state water board estimates that cleaning up all contaminated water systems to the proposed legal limit will cost about $34 million annually.

Quote by Andia Ventura

For smaller Valley communities, where many residents are lower-income farm workers and where water rates are already some of the highest in the state, the cost of cleaning up their water systems to meet the state standard would be prohibitive without compensation from Dow and Shell.

In Lamont, a town of about 20,000 just south of Bakersfield, a settlement from the companies is paying for the installation of a filtration system that uses carbon in the form of crushed coconut shells to absorb TCP before the water is piped into residents' homes. But the neighboring town of Arvin, which has a slightly larger population, is still waiting for its day in court.

"To pay for the kind of filtration system that's needed, you'd be talking about raising consumer rates probably tenfold," said Raul Barraza Jr., general manager of the Arvin Community Services District, which has set up free kiosks outside its offices where residents can fill large jugs with filtered water. "This is a disadvantaged community and we try to keep the rates as low as possible, because you can't live without water.

Picture of Raul Barraza Jr., Arvin, Calif.


Raul Barraza Jr., Arvin, Calif.

“It's a tragedy that farmworkers bust their backs in the fields all day, are exposed to pesticides on the job and then, years down the road, find that their families are in danger from the same chemicals they use to make a living,” he said. “It's a disgrace, but the great thing about this country is that you can fight back. You can go to court. You can go to Sacramento or D.C. and say, 'Hey, what are you going to do about this?’”

Asha Kreiling of Community Water Center said it's inspiring to see residents of contaminated communities speak out.

"People will take time off work to travel with us to Sacramento and testify before the state water board," she said. "It's a great thing to watch: We're at the Capitol, in a room of mostly white men in suits, and these people get up in their working clothes; maybe they're speaking Spanish, but they make their voices known."

Bartolo Chavez, who came to the San Joaquin Valley from Mexico 27 years ago and is putting two daughters through college by working the fields, was among the Arvin residents who went to Sacramento last year to urge the Water Resources Control Board to set a health-protective legal limit for TCP.

Picture of Bartolo Chavez, Arvin, Calif.


Bartolo Chavez, Arvin, Calif.

“I'm here to ask you to address an issue that is a matter of life and death,” he said to the board through an interpreter. “It's a very serious matter because we want to leave a better way of life for our children. Shell and Dow are responsible, and we want them to take responsibility. But we also need your help. You have the power in your hands to provide clean drinking water for all the people of the San Joaquin Valley.”

Chavez was recently asked if he thought his testimony made a difference.

“I told them the truth,” he said. “They heard me. I don't know if they listened. But that’s what they are paid to do.”

1 California Office of Environmental Health Hazard Assessment, Public Health Goals for Chemicals in Drinking Water: 1,2,3 Trichloropropane. Aug. 20, 2009. Available at

2 Dioxins are a group of extremely toxic persistent organic pollutants. “Dioxin” generally refers to 2,3,7,8-tetrachlorodibenzo-p-dioxin, or TCDD, the primary ingredient in the notorious defoliant Agent Orange, used by the U.S. military in vast quantities during the Vietnam War. California’s public health goal for TCDD is 14,000 times lower than that for TCP.

3 National Toxicology Program, Toxicology and Carcinogenisis of 1,2,3-Trichloropropane (CAS No. 96-18-4) in F344/N Rats and B6C3F1 Mice (gavage studies). August 1993. Available at

4 National Toxicology Program, 1,2,3-Trichloropropane, Report on Carcinogens, Eleventh Edition. 2004. Available at

5 California Office of Environmental Health Hazard Assessment, The Proposition 65 List. Updated Jan. 27, 2017. Available at

6 Sasha Khoka, There's a Cancer-Causing Chemical in My Drinking Water, But California isn't Regulating It. KQED Science, March 7, 2016. Available at

7 U.S. Environmental Protection Agency, Technical Fact Sheet – 1,2,3-TCP. January 2014. Available at

8 U.S. Environmental Protection Agency, Occurrence Data for the Unregulated Contaminant Monitoring Rule, UCMR 3 (2013-2015). Available at

9 Hawaii Department of Health, Contaminant Regulated by the Safe Drinking Water Branch. July 10, 2014. Available at

10 New Jersey Drinking Water Quality Institute, Maximum Contaminant Level Recommendations for 1,2,3-Trichloropropane in Drinking Water. Oct. 5, 2016. Available at

11 California State Water Resources Control Board, 1,2,3-Trichloropropane. Updated March 3, 2017. Available at

12 C.J. Shepherd, Tainting of Tobacco by a Dichloropropene-Dichloropropane Soil Fumigant. Nature, Dec. 20, 1952.

13 Complaint for Damages and Other Relief, East Niles Community Services District vs. The Dow Chemical Company et al., No. CGC-15-545026 (Cal. Super. Ct. Mar. 30, 2015). 

14 7 C.F.R. § 162.103(c)(1)-(2)(1949).

15 Shell Oil Company, Correspondence from F.W. Hatch to G.W. Huldrum and E.E. Heurmath. D-D Ingredient Statement. May 4, 1949.

16 Shell Oil Company Interoffice Memorandum, J.C. Willett to R.D. Mullineauz et al., Subject: D-D Soil Fumigant Options. Jan. 20, 1983.

17 The Dow Chemical Company’s and Dow Agrosciences LLC’s Verified Answer and Affirmative Defenses to Plaintiff’s Complaint For Damages and Other Relief, East Niles Community Services District vs. The Dow Chemical Company, et al., No. SCVSS120627 (Cal. Super. Ct. July 28, 2015).

18 Defendant Shell Oil Company's Verified Answer to Plaintiff East Niles Community Services District's Complaint, East Niles Community Services District vs. The Dow Chemical Company, et al., No. SCVSS120627 (Cal. Super. Ct. Aug. 20, 2015).

19 Tara Lohan, California Set to Regulate Carcinogen in Water for Decades. News Deeply, March 4, 2017. Available at

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