EWG's Tap Water Database — 2021 UPDATE



Orchard Dale Water District

1,4-Dioxane is a solvent classified by the EPA as a likely human carcinogen. It contaminates groundwater in many states due to industrial wastewater discharges, plastic manufacturing runoff and landfill runoff. Read More.

Animal studies show that 1,4-dioxane can target the liver, kidneys and respiratory system, and that prenatal exposure can harm the developing fetus. The State of California has set a Public Heatlh Goal of no more than 1 part per billion of 1,4-dioxane in drinking water. The state of Massachusetts sets a legal limit of 0.3 ppb, and New Hampshire's limit is 3 parts per billion. There is no national drinking water standard for this contaminant.

Click here to read more about 1,4-dioxane.





Samples exceeding legal limit (MCL)


Samples exceeding
health guidelines

Testing results - average by year

YearAverage resultSamples takenDetectionsRange of results
20140.873 ppb440.740 ppb - 1.10 ppb
20151.12 ppb65ND - 1.50 ppb
20161.28 ppb441.20 ppb - 1.40 ppb
20171.04 ppb108ND - 1.60 ppb
20181.35 ppb881.000 ppb - 1.80 ppb
20191.11 ppb87ND - 1.50 ppb

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 0.35 ppb

The EWG Health Guideline of 0.35 ppb for 1,4-dioxane was defined by the Environmental Protection Agency as a one-in-a-million lifetime risk of cancer. Values greater than one-in-a-million cancer risk level can result in increased cancer cases above one in a million people.

ppb = parts per billion

All test results

Date Lab ID Result
2014-06-304F30047-01A1.10 ppb
2014-06-304F30047-03A0.810 ppb
2014-12-104L11085-03A0.740 ppb
2014-12-104L11085-01A0.840 ppb