Arsenic: facts & figures

Arsenic levels in the U.S. population


Total urinary arsenic levels in the U.S. population

Urinary arsenic in mcg per gram of creatinine for people 6 years and older. Data source: National Health and Nutrition Examination Survey.

The median is the urinary arsenic level that 50% of people tested fall above and 50% of people tested fall below. The 95th percentile is the urinary arsenic level that 95% of people fall below. It shows arsenic levels in the most highly exposed people.

The increase in the 95th percentile is due mostly to an increase in organic arsenic, the type found in fish that is less harmful to health. It’s not clear why this occurred in 2009-2010.


Organic and inorganic arsenic levels in the U.S. population

Data source: Caldwell et al. (2009). Levels of urinary total and speciated arsenic in the US population: National Health and Nutrition Examination Survey 2003-2004. J Expo Sci Environ Epidemiol. 19(1): 59-68. doi: 10.1038/jes.2008.32.

When people are divided into groups based on their total arsenic exposure, we see that those with total exposure less than 50 mcg/L are exposed to mostly inorganic arsenic. Individuals with total exposure of 50 mcg/L or higher are exposed to mostly organic arsenic, the less toxic form usually found in seafood. A possible explanation for this difference is that some people test high for total arsenic exposure because they have recently consumed fish or shellfish. In order to tell if this is the case for an individual with high total exposure, it is recommended that more tests are performed to determine their levels of each type of arsenic.


Total urinary arsenic in the U.S. population by race/ethnicity

Urinary arsenic in mcg per gram of creatinine for people 6 years and older. Data source: National Health and Nutrition Examination Survey, 2011-12.

Asians have higher median and 95th percentile levels of arsenic compared to other racial/ethnic groups. This is likely due, in part, to dietary patterns.


Arsenic can affect your health

Arsenic is a naturally occurring element found in the earth. Small amounts of arsenic are often measured in soil, air, drinking water, and food. In Minnesota, some drinking water sources have high levels of arsenic that must be reduced (see Drinking Water Quality).

There are two forms of arsenic:

  • Inorganic arsenic is usually found in contaminated drinking water and is linked to several health risks. This type of arsenic can be measured at low levels in certain foods such as brown seaweed and rice.
  • Organic arsenic is found mainly in fish and shellfish and is much less harmful to your health. 

Acute arsenic poisoning, resulting from the intake of large amounts of inorganic arsenic over a short period of time, can cause vomiting, diarrhea, and sometimes death.

Long-term inorganic arsenic exposure has been linked to skin problems, heart disease, and some cancers.

Biomonitoring shows levels of arsenic in the body

Biomonitoring measures the amount of arsenic in people's blood, hair, fingernails, and urine. Urinary arsenic levels reflect recent exposures but not necessarily long-term exposures.

Data are from the National Health and Nutrition Examination Survey (NHANES). For NHANES reporting purposes, urinary arsenic levels are classified as:

  • Normal: ≤50 micrograms per liter (mcg/L)
  • High normal: >50 to <200 mcg/L
  • High: ≥200 mcg/L

What is being done about arsenic in Minnesota?

The MDH Drinking Water Protection Program ensures that all public water supplies have arsenic levels at or below the federal Safe Drinking Water Act standard.

The MDH Well Management Program provides private well owners with information on how to ensure that their water is safe to drink, including how to test for arsenic and treat their well water if arsenic is found.

MDH conducted the South Minneapolis Children's Arsenic Study, a biomonitoring project that measured arsenic levels in children's urine after high amounts of arsenic were discovered in local soil.

MDH also conducted the Minnesota Arsenic Research Study, a project that measured arsenic levels in drinking water and biomarkers for private well owners in western Minnesota.