Important Facts for Drinking Water: Arsenic

Definition

__Mean Arsenic Levels for Utah__[[br]] 1) Yearly distribution of number of community water systems (CWS) by mean arsenic concentration (cut-points: <=10, >10 ug/L arsenic, Not Detected ug/L arsenic) 2) Yearly distribution of number of people served by CWS by mean arsenic concentration (cut-points: <=10, >10 ug/L arsenic, Not Detected ug/L arsenic) __Maximum Arsenic Levels for Utah__[[br]] 3) Yearly distribution of number of CWS by maximum arsenic concentration (cut-points: <=10, >10 ug/L arsenic, Not Detected ug/L arsenic) 4) Yearly distribution of number of people served by CWS by maximum arsenic concentration (cut-points: <=10, >10 ug/L arsenic, Not Detected ug/L arsenic)

Numerator

1) Count of community water systems categorized by mean arsenic concentration for each year reported 2) Number of people served by community water systems categorized by mean arsenic concentration for each year reported 3) Count of community water systems categorized by maximum arsenic concentration for each year reported 4) Number of people served by community water systems categorized by maximum arsenic concentration for each year reported

Denominator

Not applicable.

Data Interpretation Issues

Some community water systems with higher average arsenic levels are due to higher levels in earlier years before the arsenic standard was changed. Some of these arsenic levels have since been lowered. Data reported to other sources, such as the U.S. Environmental Protection Agency, may differ slightly. This data does not include information about private water sources such as well water or tribal water systems. These calculations include all available data which varies by year and water system. Population data for each community water system are estimated based on number of connections. Inconsistent outliers and other data errors were not included in calculations in order to provide a more accurate representation of water quality. A community water system is a public water system that serves at least 15 service connections used by year-round residents or regularly serves at least 25 year-round residents. Measures do not account for the variability in sampling, numbers of sampling repeats, and variability within systems. Concentrations in drinking water cannot be directly converted to exposure because water consumption varies from person to person, including other factors such as climate, level of physical activity, and medical conditions that require increased water intake (EPA 2004). Due to errors in estimating populations, the measures may overestimate or underestimate the number of affected people. (From National Environmental Public Heath Tracking Network [NEPTHN] Nationally Consistent Data and Measures [NCDM] arsenic indicator document version 5)

Why Is This Important?

People drink and use water every day. The majority of Americans are provided with high quality drinking water. About 90% of people in the U.S. get their water from a community water system versus a smaller water supply, such as a household well. The U.S. Environmental Protection Agency (EPA) sets regulations for treating and monitoring drinking water delivered by community water systems. Currently, there are water quality standards and monitoring requirements for over 90 contaminants. Drinking water protection programs play a critical role in ensuring high quality drinking water and protecting the public's health. Because people drink and use water every day, contaminants in drinking water have the potential to affect many people. The number of people served by a community water system varies from as low as 25 to hundreds of thousands. Community water systems in the U.S. provide among the highest quality drinking water in the world. However, some contaminants are present at low levels and it is still possible that drinking water can become contaminated at higher levels. If a person is exposed to a high enough level of a contaminant, they may become ill. Arsenic is a toxic chemical element that is naturally found in the Earth's crust such as soil, rocks, and minerals. There is a wide variation in the levels of arsenic found in drinking water systems and private water supplies across the nation. The majority of health risks of arsenic exposure over time are long-term, although some short-term exposures at high doses can also cause adverse health effects. People who drink water containing arsenic in excess of regulatory standards over many years can experience a variety of health problems that include thickening and discoloration of the skin; stomach pain; nausea; vomiting; diarrhea; liver problems; cardiovascular, pulmonary, immunological, neurological, reproductive, and endocrine problems; and cancer of the bladder, skin, kidney, liver, and lung. Before 2006, community water systems were not supposed to exceed 50 micrograms of arsenic per liter. In 2006, this standard changed and currently community water systems are not supposed to exceed 10 micrograms of arsenic per liter in order to reduce adverse health effects from arsenic exposures. Arsenic compounds (As [III] and As [V]) are found in both ground water and surface waters. The primary sources are geologic formations where arsenic can be dissolved. Higher levels of arsenic tend to be found in ground water (aquifers) as compared to surface waters, such as lakes and rivers. (Modified from National Environmental Public Heath Tracking Network [NEPTHN] Nationally Consistent Data and Measures [NCDM] arsenic indicator document version 5)