TCP in California's Drinking Water

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1,2,3-TCP: A tragedy that could have been avoided

In the 1940s, the agricultural divisions of Dow Chemical and Shell started selling two soil fumigants under the trade names of D-D and Telone to help farmers manage crop damaging nematodes. Because pesticides are meant to kill living organisms, they are by their nature, toxic. However one chemical in D-D and Telone was particularly toxic to humans and persistent in the environment - 1,2,3-TCP, or Trichloropropane (TCP).

Ironically, TCP was not the ingredient that killed the nematodes. It was instead a contaminant that occurred in the manufacture of the fumigants. While it was easily removable before the products went to market, Dow and Shell chose instead to leave it in and simply – and deceptively– registered it as an active ingredient. In other words, they falsely claimed that the contaminant was necessary to the effectiveness of their products. This was despite the fact that the companies already had scientific evidence that the chemical was dangerous to humans.

TCP was banned from use in soil fumigants in the 1990s. By this time D-D had been taken off the market and Telone was reformulated. However, because the chemical does not bind to soil or break down easily in the environment, much of it had leached into groundwater over the decades and contaminated drinking water wells. Thousands of Californians are drinking and cooking with TCP just because two companies – who knew it was both dangerous and unnecessary to their product – simply didn’t bother to remove it.

So what is 1,2,3 –TCP?

1,2,3, TCP is an exclusively man-made chlorinated hydrocarbon commonly used as an industrial solvent, cleaner, and degreaser, as well in the production of paint thinners and varnish removers. TCP is also used in the production of other chemicals, which is how it became a contaminant in two commonly used soil fumigants used in California to manage nematodes.

Because TCP containing fumigants were extensively used in California, particularly in Kern, Tulare, and Fresno Counties, contamination of drinking water wells became widespread in those parts of the state.

Health impacts

In 1999, the TCP was added to the list of chemicals known to the State of California to cause cancer. Exposure can occur from drinking or cooking with TCP-contaminated water and from inhaling its steam (such as while showering or washing dishes). Exposure may possibly occur from dermal contact as well. Contact with very high concentrations of TCP may irritate or burn the skin, nose, eyes, or throat, and it may cause drowsiness or liver damage. At this stage, it appears that TCP is unlikely to become concentrated in food, such as plants and fish.

In 2009, the Office of Environmental Health Hazard Assessment adopted a Public Health Goal for TCP in drinking water of .0007 parts per billion (ppb) -- one of the most stringent ever established in the state – because of studies showing it to be extremely toxic at low levels. A Public Health Goal is the level in water at which no significant public health impacts are expected. It is not an enforceable standard.

How big is the problem?

Through 2013, detections of 1,2,3-TCP in two or more samples were reported in 372 active and standby sources, belonging to 92 water systems in 17 counties.

This map was produced by KQED, drawing on information from the State Water Resources Control Board. It shows water systems where significant levels of the 123-TCP have been detected. Image courtesy KQED, whose reporter, Sasha Khokha, recently found her own water supply to be contaminated as part of a story on this issue.

Water systems where significant levels of contaminant 123-TCP have been detected.

Needed solution: Establish a drinking water standard.

Despite the dangers of TCP, there is no enforceable drinking water standard for it at either the federal or state level. Consequently, water providers are not required to treat TCP contaminated water, consumers can continue to be exposed, and it is difficult to hold the responsible parties (Shell and Dow) accountable.

Clean Water Action has launched a new campaign to ensure that California establishes a drinking water standard, also called a Maximum Contaminant Level or MCL for TCP. It is up to the state Division of Drinking Water (DDW), under the auspices of the State Water Resources Control Board to establish a standard as close to the Public Health Goal as is technically and economically feasible. Clean Water Action is calling on the Board to set the standard at .005 ppb, which is the lowest level at which TCP can currently be detected (this is what is meant by technically feasibility). Cost of water treatment should not be a limiting factor in setting the most stringent standard possible because the price tag would be paid by Shell and Dow, and not the local water systems.

Where are we now?

The dual goals of Clean Water Action’s campaign are to 1) ensure the DDW establishes a TCP drinking water standard by spring 2017 and 2) to advocate that the standard is the most protective that is technically possible, i.e., 5ppt.

We have already made tremendous progress. Clean Water Action has helped create an effective and growing collaborative campaign with other water advocates and impacted communities, met with DDW staff and all members of the State Water Resources Control Board, got a public hearing on the drinking water program, and spoke publicly on the need to act now on this dangerous contaminant. The result is a commitment by the State Board to create the standard by April 2017, and work has already begun on the required economic and technical analyses.

This article from Pacific Standard Magazine covers some recent developments in our campaign.

This article contains more information on Dow related to this issue. 

This article from Bakersfield Now delves into contamination in the area.

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