WELLOG ARSENIC IN WELL WATER

What is Arsenic?

Arsenic is a natural element that has had a long reputation for its toxicity. Simply stated, arsenic is poisonous to humans and other animals. A one-time oral dose of 60 milligrams of inorganic arsenic is considered fatal for most people. This amount is about 1/50 of the weight of a penny.

Drinking water having 10 micrograms per liter (10 parts per billion) or less of arsenic content is considered acceptable.

Where does Arsenic come from?

Arsenic is found in many areas of the world and is a relatively common element in many rock formations within the earth. Arsenic is associated with certain mineralized areas and shale formations. A geophysical gamma-ray log can yield information about the layers of earth the well was drilled through and identify potential shale and clay layers and their association with sandstone layers that are possible aquifers.

Arsenic was at one time used as a pesticide in agriculture. Shallow wells are more susceptible to having arsenic contamination from prior agricultural operations. Deeper wells often have layers of clay that protect the well from upper aquifer contamination.

Arsenic is also presently used to treat lumber which is probably not an issue for water wells.

How does Arsenic get into drinking water?

Arsenic has the ability to be dissolved into water, a process called leaching. Once arsenic is in solution with water, it may be transported with the movement of water to a water well. People consuming water from a well that is contaminated with arsenic may develop health problems. The Environmental Protection Agency, World Health Organization and others have determined a significant health risk exists when levels of arsenic in water exceed 10 parts per billion (ppb), .010 milligrams per liter or 10 micrograms per liter.

What is the probability of Arsenic in my well?

Practically every well has arsenic in the water. For example in 44 commercial water wells in Pinal County, Arizona, all 44 have varying amounts of arsenic. The amounts vary from as low as 2 micrograms per liter (2 ppb) to as high as 42 micrograms per liter (42 ppb) based on best estimates from sample data given to EPA. The mean level of the 44 wells is 9.55 micrograms per liter (9.55 ppb). The standard deviation is 8.00 which means 68 percent of the wells are between 5.55 ppb and 13.55 ppb.

Compare with other counties in Arizona:

Maricopa County, Arizona

Cochise County, Arizona

Are there other sources of inorganic Arsenic?

Food and water are the primary sources of intake of inorganic arsenic. EPA estimates the average dietary intake of arsenic per day is 14 micrograms above the amount consumed from water. Considering an average intake of 2 liters of water per day for an adult, water would likely be the primary source of arsenic. However, since the normal levels should be much lower, food is more likely to be the primary source. Examples of foods likely to be high in arsenic are uncooked rice, grape juice, flour and cooked spinach.

Should I test my well for Arsenic?

Arsenic occurs in most water wells. The question is to what level. How much arsenic is in your water well? Since arsenic has no taste or odor in water, the best way of finding out is to collect a sample in an approved, sealed water sample container. The next step is to have the water analyzed at a certified testing laboratory. The cost of testing is usually under $40.00. If no arsenic is detected, it isn’t usually necessary to conduct further testing. If arsenic is detected at levels greater than 10 micrograms per liter, it is advisable to conduct a second test and not use the water for drinking or cooking. Use an alternate source of water or install a treatment system.

What are the methods used to reduce arsenic levels in drinking water?

Install a treatment system

Depending on the amount of arsenic that is in the water, a treatment system may or may not work with enough efficiency to lower the level to safe level for drinking. It is important to contact a reliable dealer that can properly install a treatment system and establish a regular process to monitor arsenic levels. A conventional water softener, chlorinator, or activated charcoal filter will not remove arsenic.

Drill a new well

It may be necessary to drill a new well. A new well drilled into a different water producing zone may have reduced arsenic levels.

Connect to a public water system

Community water systems will be required to maintain arsenic levels at or below 10 micrograms per liter (10 ppb) beginning in January of 2006. These systems are tested on a routine basis.

Buy bottled water

Bottled water is an important alternative. Note: Bottled water is not regulated by EPA in terms of arsenic. It is advisable therefore to ask your bottled water dealer for information about their standards and testing for arsenic.