Chlorate

Artesian Water Company

Chlorate forms in drinking water as a byproduct of disinfection. Chlorate impairs thyroid function, making chlorate exposure most harmful during pregnancy and childhood. Read More.

In 2002, California scientists proposed an advisory value, called an action level, for chlorate at 200 parts per billion. Between 2013 and 2015, the EPA collected data through the Unregulated Contaminant Monitoring Rule program and found that over 15 percent of water tests from 38 percent of utilities had chlorate levels above a health-protective concentration, which federal scientists defined as 210 parts per billion, nearly equivalent to the California advisory value.

Click here to read more about disinfection byproducts.

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Samples

Samples exceeding legal limit (MCL)

Samples exceeding
health guidelines

Testing results - average by year

Year	Average result	Samples taken	Detections	Range of results
2013	25.8 ppb	24	13	ND - 170.0 ppb
2014	19.5 ppb	24	11	ND - 130.0 ppb
2015	N/A	0	0	N/A
2016	N/A	0	0	N/A
2017	N/A	0	0	N/A
2018	N/A	0	0	N/A
2019	N/A	0	0	N/A

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 210 ppb

The EWG Health Guideline of 210 ppb for chlorate was defined by the Environmental Protection Agency as a benchmark for testing under the Unregulated Contaminant Monitoring Rule program. This health guideline protects against hormone disruption.

ppb = parts per billion

All test results

Date	Lab ID	Result
2013-07-17	2860261	ND
2013-07-17	2860447	ND
2013-07-17	2860439	23.0 ppb
2013-07-17	2860435	21.0 ppb
2013-07-17	2860761	20.0 ppb
2013-07-17	2860419	ND
2013-07-17	2860932	ND
2013-07-17	2860388	20.0 ppb
2013-07-17	2860377	ND
2013-07-17	2860349	22.0 ppb
2013-07-17	2860943	ND
2013-07-17	2860197	51.0 ppb
2013-07-17	2860839	ND
2013-07-17	2860774	52.0 ppb
2013-07-17	2860819	ND
2013-07-17	2860746	170.0 ppb
2013-07-17	2860888	110.0 ppb
2013-07-17	2860511	21.0 ppb
2013-07-17	2860803	51.0 ppb
2013-07-17	2860338	27.0 ppb
2013-10-15	2913849	ND
2013-10-15	2913515	ND
2013-10-15	2913519	ND
2013-10-15	2913523	31.0 ppb
2014-01-28	2964034	ND
2014-01-28	2963997	ND
2014-01-28	2963993	ND
2014-01-28	2964091	21.0 ppb
2014-01-28	2964187	130.0 ppb
2014-01-28	2964217	34.0 ppb
2014-01-28	2964129	53.0 ppb
2014-01-28	2964075	28.0 ppb
2014-01-28	2964060	ND
2014-01-28	2964273	24.0 ppb
2014-01-28	2964256	24.0 ppb
2014-01-28	2964147	43.0 ppb
2014-01-28	2964206	49.0 ppb
2014-01-28	2964164	22.0 ppb
2014-01-28	2964041	ND
2014-01-28	2964244	ND
2014-01-28	2964231	ND
2014-01-28	2964114	ND
2014-01-28	2964103	ND
2014-04-23	3014333	ND
2014-04-23	3014022	ND
2014-04-23	3014032	ND
2014-04-23	3014018	ND
2014-07-16	3064489	40.0 ppb