WELLOG ARSENIC IN WELL WATER
Revised
© 2005-2008 WELLOG
All Rights Reserved
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 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,
Compare with other counties in
Maricopa
County,
Cochise
County,
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?
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.
Should I be concerned about other things in my water?
It is important to test for bacteria at least once per year or any time a change in color or odor of water occurs.
Nitrate contamination is another potential problem that should be tested for annually.
Lead contamination can occur when water stands in pipes for long periods of time. Old lead pipes, copper pipes soldered with lead may cause lead contamination.
Volatile Organic Contaminants (VOC) sometimes occur. If a well is located near an area that is used for commercial purposes where fuel or oil could possibly enter the ground water, it is advisable to have your water tested. Pesticides used around agricultural areas often are found in local water wells. Again, shallow wells have greater potential for pesticide contamination.
Old unused wells present a possible entry point for contamination of aquifers. A well that has out lived it’s useful life should be properly sealed and abandoned. A closing video inspection should be performed immediately prior to shutting in the well with cement.
Where can I get additional advice or help?
WELLOG has tools to properly sample well water. When your pump is removed for service, ask WELLOG to perform a video inspection of your well. Gamma ray logging can identify locations of clay and sandstone formations. If a well is producing water from several formations, it is a good idea to sample water in the well at several depths. Fluid resistivity tests can provide added information about areas in the well that are producing contaminants in the form of Total Dissolved Solids (TDS). Remedial plans can be suggested and acted on to seal certain areas from producing water. WELLOG can perform initial sample testing and/or transport samples to certified laboratories.
