Biomonitoring in Washington State

South Whidbey Island - High Arsenic Area Study

South Whidbey Island is one of several areas in the state known to have higher levels of naturally occurring arsenic in groundwater. From July – September 2011, Washington Environmental Biomonitoring Survey (WEBS) staff collected urine and drinking water samples from residents on private wells or small water systems (less than 15 connections). The objective of this biomonitoring project was to measure the levels of total and speciated arsenic in the urine of people living in an area with high levels of naturally occurring arsenic in groundwater. Twelve other metals were also measured in urine samples.

See High Arsenic Area Study Brochure (PDF) for more information


A total of 172 participants were recruited for this project and tap water samples were tested from 82 households.


Arsenic and metal levels in urine were compared with general population statewide levels collected in 2010 and 2011 (see above). In addition to the urine testing, total arsenic was measured in drinking water collected from participating households. Testing results were reported to participants in a letter about eight weeks after sample collection.

Major Findings

  • Urine levels of total arsenic were higher for South Whidbey (28.4 μg/g creatinine) compared to statewide and national levels.
  • 28 percent of participants had urine arsenic levels above CDC's reporting level.
  • 54 percent of water samples retested at the laboratory were above the EPA's standard.
  • Arsenic from seafood and tap water contributed to higher arsenic levels in urine.