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EWG's Tap Water Database — 2019 UPDATE

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Total trihalomethanes (TTHMs)

Salt Lake City Water System

Trihalomethanes are cancer-causing contaminants that form during water treatment with chlorine and other disinfectants. The total trihalomethanes group includes four chemicals: chloroform, bromodichloromethane, dibromochloromethane and bromoform. Read More.

Studies conducted in the U.S. and Europe have found that drinking tap water that carries disinfection byproducts increases the risk of developing bladder cancer. In animal studies, all trihalomethanes cause liver, kidney and intestinal tumors. Some human epidemiological studies also reported an association between disinfection byproducts and an increased risk of problems during pregnancy, including spontaneous miscarriage, cardiovascular defects, neural tube defects and low birth weight.

The health guideline of 0.15 parts per billion, or ppb, for the group of four trihalomethanes, or THM4/TTHM, was defined in a peer-reviewed scientific study by EWG and represents a one-in-one-million lifetime cancer risk level.

Click here to read more about disinfection byproducts.

 

280

Samples

4

Samples exceeding legal limit (MCL)

253

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
201242.5 ppb61610.600 ppb - 69.2 ppb
201329.1 ppb38380.800 ppb - 61.7 ppb
201430.7 ppb5749ND - 75.5 ppb
201517.9 ppb2515ND - 60.8 ppb
201635.8 ppb5243ND - 92.0 ppb
201736.5 ppb47479.05 ppb - 64.7 ppb

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 0.15 ppb

The health guideline of 0.15 parts per billion, or ppb, for the group of four trihalomethanes, or THM4/TTHM, was defined in a peer-reviewed scientific study by EWG and represents a one-in-one-million lifetime cancer risk level.

EPA Maximum Contaminant
Level (MCL) 80 ppb

The legal limit for the group of four trihalomethanes, established in 1998, was based on the need for residual disinfectant levels in water served to customers and the cost of treatment. This limit does not fully protect against the risk of cancer due to exposure to trihalomethanes.

ppb = parts per billion

All test results

Date Result
2012-01-2460.2 ppb
2012-01-2462.3 ppb
2012-01-2463.1 ppb
2012-01-2469.2 ppb
2012-01-2460.1 ppb
2012-01-2461.3 ppb
2012-01-2461.6 ppb
2012-01-2458.0 ppb
2012-01-2418.8 ppb
2012-01-2426.5 ppb
2012-01-2418.5 ppb
2012-01-2442.4 ppb
2012-04-2445.4 ppb
2012-04-2431.1 ppb
2012-04-2432.7 ppb
2012-04-2432.4 ppb
2012-04-2433.5 ppb
2012-04-2436.3 ppb
2012-04-2436.0 ppb
2012-04-2431.1 ppb
2012-04-2431.1 ppb
2012-04-2417.5 ppb
2012-04-2423.1 ppb
2012-04-2433.5 ppb
2012-06-290.600 ppb
2012-07-2539.5 ppb
2012-07-2528.3 ppb
2012-07-2542.3 ppb
2012-07-2541.9 ppb
2012-07-2549.4 ppb
2012-07-2548.7 ppb
2012-07-2546.0 ppb
2012-07-2547.2 ppb
2012-07-2547.0 ppb
2012-07-2546.9 ppb
2012-07-2530.9 ppb
2012-07-2519.0 ppb
2012-10-0243.4 ppb
2012-10-0244.4 ppb
2012-10-0245.2 ppb
2012-10-0224.0 ppb
2012-10-0262.3 ppb
2012-10-0257.8 ppb
2012-10-0223.7 ppb
2012-10-0244.4 ppb
2012-10-0244.8 ppb
2012-10-0251.4 ppb
2012-10-0252.9 ppb
2012-10-0241.8 ppb
2012-11-1348.7 ppb
2012-11-1324.2 ppb
2012-11-1345.3 ppb
2012-11-1344.5 ppb
2012-11-1356.3 ppb
2012-11-1354.6 ppb
2012-11-1346.2 ppb
2012-11-1349.8 ppb
2012-11-1353.7 ppb
2012-11-1353.7 ppb
2012-11-1342.9 ppb
2012-11-1362.9 ppb
2013-01-187.20 ppb
2013-02-1725.6 ppb
2013-02-1727.5 ppb
2013-02-1724.3 ppb
2013-02-1731.7 ppb
2013-02-1724.0 ppb
2013-02-1727.4 ppb
2013-02-1715.5 ppb
2013-02-1715.6 ppb
2013-02-1715.5 ppb
2013-02-1714.6 ppb
2013-02-1715.2 ppb
2013-02-1725.7 ppb
2013-04-3037.3 ppb
2013-04-3026.1 ppb
2013-04-3029.3 ppb
2013-04-3028.5 ppb
2013-04-3032.0 ppb
2013-04-3030.1 ppb
2013-04-3029.0 ppb
2013-04-3029.2 ppb
2013-04-3029.5 ppb
2013-04-3030.8 ppb
2013-04-3029.5 ppb
2013-04-3027.9 ppb
2013-06-180.800 ppb
2013-09-1761.7 ppb
2013-09-1736.7 ppb
2013-09-1740.8 ppb
2013-09-1740.6 ppb
2013-09-1747.3 ppb
2013-09-1751.0 ppb
2013-09-1750.0 ppb
2013-09-1719.0 ppb
2013-09-1718.3 ppb
2013-09-1728.7 ppb
2013-09-1727.6 ppb
2013-09-1753.3 ppb
2014-01-10ND
2014-02-2524.6 ppb
2014-02-2523.7 ppb
2014-02-2534.2 ppb
2014-02-2524.0 ppb
2014-02-2527.5 ppb
2014-02-2512.6 ppb
2014-02-2512.1 ppb
2014-02-2515.4 ppb
2014-02-2517.4 ppb
2014-02-2520.4 ppb
2014-02-2531.8 ppb
2014-02-2529.8 ppb
2014-04-2940.8 ppb
2014-04-2938.2 ppb
2014-04-2926.0 ppb
2014-04-2930.0 ppb
2014-04-2925.5 ppb
2014-04-2942.5 ppb
2014-04-2921.2 ppb
2014-04-2921.0 ppb
2014-04-2912.8 ppb
2014-04-2917.2 ppb
2014-04-2923.9 ppb
2014-04-2935.9 ppb
2014-05-30ND
2014-06-03ND
2014-06-06ND
2014-06-112.30 ppb
2014-06-25ND
2014-07-01ND
2014-07-02ND
2014-07-09ND
2014-07-110.500 ppb
2014-08-0548.2 ppb
2014-08-0544.8 ppb
2014-08-0550.9 ppb
2014-08-0548.4 ppb
2014-08-0550.1 ppb
2014-08-0544.2 ppb
2014-08-0544.3 ppb
2014-08-0544.6 ppb
2014-08-0527.2 ppb
2014-08-0536.6 ppb
2014-08-0536.9 ppb
2014-08-0549.9 ppb
2014-10-2175.5 ppb
2014-10-2153.5 ppb
2014-10-2170.1 ppb
2014-10-2164.3 ppb
2014-10-2169.8 ppb
2014-10-2165.6 ppb
2014-10-2132.7 ppb
2014-10-2136.1 ppb
2014-10-2150.3 ppb
2014-10-2139.6 ppb
2014-10-2157.4 ppb
2015-01-30ND
2015-02-276.40 ppb
2015-05-08ND
2015-05-15ND
2015-06-19ND
2015-06-29ND
2015-06-300.733 ppb
2015-07-07ND
2015-07-100.200 ppb
2015-08-07ND
2015-09-04ND
2015-09-18ND
2015-09-29ND
2015-10-2750.9 ppb
2015-10-2722.5 ppb
2015-10-2732.2 ppb
2015-10-2731.9 ppb
2015-10-2758.6 ppb
2015-10-2760.8 ppb
2015-10-2739.2 ppb
2015-10-2739.6 ppb
2015-10-279.10 ppb
2015-10-279.70 ppb
2015-10-2738.5 ppb
2015-10-2748.0 ppb
2016-01-084.55 ppb
2016-01-151.20 ppb
2016-01-2636.3 ppb
2016-01-2632.1 ppb
2016-01-2636.0 ppb
2016-01-2637.7 ppb
2016-01-2637.2 ppb
2016-01-2632.4 ppb
2016-01-2621.0 ppb
2016-01-2620.2 ppb
2016-01-2625.1 ppb
2016-01-2638.4 ppb
2016-01-2625.9 ppb
2016-01-2634.2 ppb
2016-02-125.50 ppb
2016-02-26ND
2016-03-25ND
2016-05-180.500 ppb
2016-05-19ND
2016-06-03ND
2016-06-10ND
2016-06-24ND
2016-06-281.000 ppb
2016-07-010.800 ppb
2016-07-08ND
2016-07-13ND
2016-07-2762.5 ppb
2016-07-2756.6 ppb
2016-07-2756.5 ppb
2016-07-2730.3 ppb
2016-07-2761.1 ppb
2016-07-2764.0 ppb
2016-07-2761.1 ppb
2016-07-2756.5 ppb
2016-07-2757.6 ppb
2016-07-2741.1 ppb
2016-07-2763.4 ppb
2016-07-2759.4 ppb
2016-07-290.200 ppb
2016-08-05ND
2016-10-0491.6 ppb
2016-10-0492.0 ppb
2016-10-0478.3 ppb
2016-10-0463.4 ppb
2016-10-0482.5 ppb
2016-10-0491.7 ppb
2016-10-0455.4 ppb
2016-10-0454.0 ppb
2016-10-0433.9 ppb
2016-10-0455.5 ppb
2016-10-0448.4 ppb
2016-10-0455.9 ppb
2017-01-1033.9 ppb
2017-01-1019.5 ppb
2017-01-1021.8 ppb
2017-01-1013.6 ppb
2017-01-1013.6 ppb
2017-01-1015.8 ppb
2017-01-1017.3 ppb
2017-01-1024.8 ppb
2017-01-1019.5 ppb
2017-01-1019.5 ppb
2017-01-169.05 ppb
2017-04-2515.5 ppb
2017-04-2537.9 ppb
2017-04-2538.1 ppb
2017-04-2535.2 ppb
2017-04-2549.5 ppb
2017-04-2535.2 ppb
2017-05-1664.7 ppb
2017-05-1621.8 ppb
2017-05-1613.6 ppb
2017-05-1619.5 ppb
2017-05-1624.0 ppb
2017-05-1619.1 ppb
2017-08-0154.7 ppb
2017-08-0139.8 ppb
2017-08-0157.8 ppb
2017-08-0157.9 ppb
2017-08-0159.6 ppb
2017-08-0161.0 ppb
2017-08-0156.5 ppb
2017-08-0156.4 ppb
2017-08-0158.7 ppb
2017-08-0158.9 ppb
2017-08-0131.6 ppb
2017-08-0149.0 ppb
2017-10-1752.5 ppb
2017-10-1741.1 ppb
2017-10-1740.9 ppb
2017-10-1741.1 ppb
2017-10-1742.1 ppb
2017-10-1753.1 ppb
2017-10-1736.0 ppb
2017-10-1738.2 ppb
2017-10-1740.1 ppb
2017-10-1740.2 ppb
2017-10-1723.0 ppb
2017-10-1742.5 ppb