1,2,3-Trichloropropane (1,2,3-TCP) in Drinking Water
In the 1930s, it was discovered that a mixture of dichloropropanes and dichloropropenes could be used as fumigant to control nematodes in agricultural settings. 1,2,3-Trichloropropane (1,2,3-TCP) was not deliberately included, but was a byproduct in the synthesis of these dichloropropanes and dichloropropenes, in the same way that 2,3,7,8-TCDD can be a trace byproduct in the synthesis of Agent Orange.
By 2005 levels of 1,2,3-TCP had become high enough in water to warrant further investigation,1 but widespread public interest in California was not sparked until March of 2016, when an investigative reporter became curious about a footnote in the report issued by her local public water utility.2 When she received the test results, she learned that the levels in her drinking water were 2.2 parts per trillion (ppt; but not to be confused with parts per thousand), more than 3X the California Office of Environmental Health Hazard Assessment (OEHHA) goal of 0.7 ppt.
Broadening her inquiry, she discovered that even though testing for 1,2,3-TCP is not mandatory by either state or federal regulations, hundreds of locations in about 100 drinking water districts in California had reported levels greater than 0.005 μg/L (5 ppt). While USEPA M1624 and subsequent methods for analyzing VOC have been in place for decades, and California has added it to Proposition 65, a list of chemicals known to the state to cause cancer or reproductive toxicity,3 in 1999, regulations are still silent. That seems likely to change in the near future, as a Maximum Contaminant Level (MCL) for TCP will be proposed by the Division of Drinking Water in 2016.4
Deuterated 1,2,3-trichloropropane (1,2,3-TCP) was first produced at CIL in the 1980s, but it had not been available when USEPA M1624 was being developed. CIL formulated a quantitative standard in 2003, DLM-2080-1.2, although analysts had been using the internal standard for years before that. An unlabeled standard, ULM-6911-1.2, is also available.