1,2,3-TCP Regulatory Update

August 4, 2016

On July 20, 2016, a regulatory team with the California State Water Resources Control Board made a preliminary recommendation of a Maximum Contaminant Limit (“MCL”) for the chemical 1,2,3-trichloropropane (also referred to as “TCP” or “1,2,3-TCP”).  The preliminary recommendation is to set the MCL at 5 parts per trillion, meaning that public water systems in California would be prohibited from serving drinking water containing more than 5 parts per trillion of TCP.  This MCL would be the most stringent water quality standard in California.  The proposed regulation will require regular testing of public drinking water sources for this chemical, many of which have never been tested or have been tested with methods that are not capable of detecting down to single-digit parts per trillion.

The preliminary recommendation of a 5 parts per trillion MCL stems out of scientific research showing numerous adverse health effects caused by TCP.  Short-term exposure may irritate eyes, skin and the respiratory tract; depress the central nervous system, and affect concentration, memory, and muscle coordination.  Long-term exposure may damage the liver and/or kidney; reduce body weight; and increase incidence of cancerous tumors.  Various government and research organizations have concluded that TCP is likely to cause cancer in humans.

Although this development represents the first major step towards an MCL for TCP in California, SL Environmental Law Group has been working on TCP contamination of groundwater since 2005.  That year, SL investigated and filed one of the first lawsuits on behalf of a water system for drinking water contamination caused by TCP.  SL learned that TCP is an exclusively man-made chemical that was an impurity in agricultural pesticides manufactured by Dow Chemical and Shell Oil and used heavily on California farmland from at least the 1950s through the mid-1980s.  Not only was the TCP unnecessary to make the pesticide work, it was not disclosed on product labeling or regulatory filings.  When farmers applied these pesticides to their fields, they unknowingly released TCP into the soil, which then migrated into the water table.  This is why many of the known incidents of TCP contamination occur in agricultural areas, such as California’s Central Valley.

Since SL filed its first TCP case, it has recovered over $30 million for water system clients from Dow and Shell.  These recoveries allow the water systems to remove TCP from their drinking water without passing those costs on to water customers.  SL also has several ongoing TCP cases and expects to achieve similarly favorable recoveries for those clients.

The regulatory team with the State Water Resources Control Board expects to present a draft rulemaking package to the Board later this year.  It will be followed by a 45-day public comment period and a public hearing.  The MCL is expected to go into effect on about July 1, 2017.

For more information, please visit the State Water Resources Control Board’s page on TCP:


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