Reducing the impacts of arsenic-contaminated soils

twitter_coverphoto_USDASoil contamination is a major concern for Greenleaf Communities. We strive to learn more about how to reduce the impact contaminants have on human health. An emerging issue is the level of arsenic found in our food, water and soil. Research underway is improving out understanding of the impacts of arsenic in food sources and developing practices to reduce the amount of arsenic in food.

Arsenic comes in two forms, organic and inorganic, with inorganic arsenic being the more harmful to human health. Inorganic arsenic is formed when arsenic combines with other elements (not including carbon). Exposure to high levels of inorganic arsenic can be detrimental to human health and has been shown to increase the likelihood of developing certain cancers and cardiovascular disease. Exposure to arsenic can occur from ingestion of arsenic-contaminated soil, drinking contaminated water, and applying pesticides that contain arsenic. Arsenic can also be found in certain foods like rice, which can contain small amounts of inorganic arsenic. [1]

Arsenic in Soil

Arsenic occurs naturally in the soil in many areas around the world, but has also contaminated soils through its past use in wood treatment, fertilizers, pesticides and herbicides. Copper-chromated arsenic (CCA) had been used as a wood preservative in residential and commercial structures. It has since been phased out in residential settings but can still be found in older structures.

Lead arsenate was a commonly used arsenical insecticide beginning in 1892. The most common use of lead arsenate was used to control moths in apple orchards. Therefore, on land that was previously used for an orchard, it is important to conduct soil testing before planting.

While multiple factors, including the soil properties, type of arsenic, and climate can impact the uptake of arsenic into the plant; it has been found that with increasing soil arsenic, plant arsenic tends to also increase. [2] Arsenic solubility and mobility can increase in flooded soils or sandy soils. In the case of rice, different varieties can uptake arsenic in differing amounts even when grown in the same soil. [3]

Arsenic in Food

Arsenic can be ingested through soil particles left on produce or through the uptake of arsenic into the plant from contaminated soil and water. Some food is higher in arsenic than others, depending on factors such as the type, variety and level of soil or water contamination.

Rice tends to be higher in arsenic than other foods because it can easily take up the compound into plant tissues. Rice uptakes silicon from the soil to help strengthen the plant. Arsenic is chemically similar to silicon under flooded conditions (like in rice paddies) that it becomes easily transported into the plant.

The FDA found that basmati rice had one of the lower concentrations of arsenic (3.5 micrograms per 1 cup cooked vs. 6.7 micrograms per 1 cup cooked non-basmati rice). The FDA recommends eating a diet that is varied to minimize potential impacts from one type of food. This advice is not only for avoiding arsenic exposure or other risks, but also because a healthy, balanced diet is always a good thing.

Research into the best ways to avoid arsenic from rice and the health impacts of arsenic in the diet is ongoing. The FDA is working with other researchers and agencies to develop the best recommendations for limiting exposure to arsenic through food sources.

After testing arsenic in juice, Consumer Reports raised concern over the levels in apple juice. This has lead to a response by the FDA who is proposing a limit for the compound in apple juices much like the current limit in water. The FDA has found that the levels in apple juice have not exceeded the 10 parts per billion limit that is set for water.

Gardening on Arsenic-contaminated Soil

Taking certain precautions can reduce the risk of ingesting arsenic and other contaminants from soil. If gardening on suspected contaminated soil, consider testing the soil for lead and arsenic concentrations.

• Wash produce from your garden before bringing it into the house if it is grown on contaminated soils, this reduces the risk that the soil will be brought into the home

• Once inside, wash produce using a vegetable wash and a scrub brush to remove any soil particles that may be left on the fruit or vegetable

• Personal hygiene should also be considered

o Wear gloves and wash hands after gardening

o Wear a set of clothing that is only used for gardening and wash separately

• Other recommendations are to change the land use of arsenic-contaminated soil by growing ornamentals or by using raised beds with non-contaminated soil.

• Be aware of the materials you are using in your garden. Do not use railroad ties or woods that have been treated with CCA in your raised beds or in the gardens.

Other lifestyle recommendations for reducing arsenic exposure are to:

• Not burn wood that has been treated with CCA

• Test well water for arsenic

• Seal decks or other wood every 6 months-2 years if it is made of CCA-treated wood

• Do not use pesticides that contain arsenic

For more information regarding arsenic ingestion prevention, please look to these resources:

Minnesota Department of Health: Arsenic

Gardening on lead- and arsenic-contaminated soils from Washington State University Cooperative Extension (PDF)

Consumer Reports findings on arsenic levels in rice products

 

 

[1] Minnesota Department of Health, 2007

[2] Peryea, 1999

[3] Guerinot et al Minnesota

Department of Health, Division of Environmental Health. 2007. Hazardous Sites and Substances: Arsenic. Retrieved from http://www.health.state.mn.us/divs/eh/hazardous/topics/arsenic.html Peryea F.J. (1999).

Gardening on lead- and arsenic- contaminated soils. Cooperative Extension, Washington State University. Retrieved from http://www.ecy.wa.gov/programs/tcp/area_wide/aw/appk_gardening_guide.pdf

Guerinot, M.L., Punshon, T., Salt, D.E. Arsenic uptake, transport and accumulation in plants. Dartmouth Toxic Metals, Superfund Research Program. Retrieved from http://www.dartmouth.edu/~toxmetal/research-projects/arsenic-in-plants.html