Chromium (total)

City of Sonoma

Chromium is a naturally occurring metal, but industrial uses can elevate its levels in water. One form, hexavalent chromium, causes cancer. Total chromium is not a good indicator of the amount of hexavalent chromium in drinking water.

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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	0.526 ppb	8	6	ND - 0.900 ppb
2014	0.329 ppb	10	6	ND - 0.660 ppb
2015	ND	1	0	ND
2016	ND	1	0	ND
2017	ND	1	0	ND
2018	0.960 ppb	1	1	0.960 ppb
2019	0.980 ppb	1	1	0.980 ppb

ppb = parts per billion

State and national drinking water standards and health guidelines

EPA Maximum Contaminant
Level (MCL) 100 ppb

The legal limit for total chromium, established in 1991, was based on a 1958 toxicity study in laboratory animals, and applies to both the less-toxic trivalent chromium and the more-toxic hexavalent chromium forms of this compound. This limit does not protect against the risk of cancer from ingestion of hexavalent chromium.

ppb = parts per billion

All test results

Date	Lab ID	Result
2013-07-18	201307190442AM	ND
2013-07-18	201307190436AM	0.530 ppb
2013-07-18	201307190446AM	0.900 ppb
2013-07-18	201307190438AM	0.900 ppb
2013-07-18	201307190448AM	0.580 ppb
2013-07-18	201307190444AM	ND
2013-07-18	201307190450AM	0.490 ppb
2013-08-22	201308230073AM	0.810 ppb
2014-01-07	201401080317AM	0.640 ppb
2014-01-07	201401080309AM	0.610 ppb
2014-01-07	201401080305AM	0.390 ppb
2014-01-07	201401080307AM	ND
2014-01-07	201401080315AM	0.630 ppb
2014-01-07	201401080319AM	0.360 ppb
2014-01-07	201401080313AM	0.660 ppb
2014-01-07	201401080311AM	ND
2014-03-17	9541-006-0920	ND
2014-09-03	9541-023-0910	ND
2015-05-13	9541-023-0920	ND
2016-03-29	9541-002-0735	ND
2017-01-09	9541-006-0000	ND
2018-10-23	9541-023-0945	0.960 ppb
2019-09-04	9541-002-1208	0.980 ppb