Arsenic and the Garden
 | Author:
Allison Kosto, MSU Broadwater County Extension Agent
MSU Broadwater County Extension Agent |
Although many people recognize arsenic as a poison, it is a naturally occurring element in soils and sedimentary rocks.
Certain types of soil and rock have higher than average arsenic levels. In Montana, higher concentrations are often found near geothermal sources such as hot springs, mined ore and some glacial geologic deposits. In Broadwater County, there is a section at the south end of the county that is known for high arsenic levels.
Often times, these areas of higher arsenic don’t cause much of an issue. However, arsenic can enter groundwater when the water flows through areas with mineral deposits high in arsenic. Groundwater that is then tapped for drinking water can be high in arsenic as well. Chronic exposure to arsenic through drinking water can result in skin problems, high blood pressure, circulatory system failure, diabetes, nervous system problems, low birth weigh and cancer.
Arsenic is tasteless and odorless so the only want to know if your water is safe to drink is through testing. MSU Extension offers well-testing kits through the Well Educated program as well as many other labs. The EPA sets a drinking water standard of 10 parts per billion for arsenic. If you water tests above this than you need a treatment system to safety drink the water.
Drinking water in the home is fairly straightforward as there has been lots of research done, and are set EPA standards along with good treatment options. However, a question arises when the water is being used for other purposes such as watering the garden or for pets or livestock. Typically water treatment systems such as reverse osmosis do not produce enough water or are not cost effective to also use outside the home.
There are a couple of different ways that garden produce could be exposed to arsenic. It can be assumed that if groundwater is high in arsenic, so is the soil. The good news is that only very small amounts of arsenic move from the soil to most plants. Rice, which isn’t grown in Montana, is an exception and is known to take up large amounts of arsenic. The other way that plants can be exposed to arsenic is through the water. If plants are irrigated with water high in arsenic, the plant tissues are potentially exposed to arsenic.
There are FDA standards for arsenic concentrations in leaves, fruits and vegetables. However, research has concluded that plants will likely die or have severely reduced yields before the plant exceeds FDA standards. Research has also shown that root crops such as radishes, potatoes and onions accumulate arsenic to a greater degree than leafy greens and above ground fruits and vegetables. However, even these plants will become unhealthy before the arsenic exceeds FDA limits.
Based on water tests that I have seen in the Wheatland area in Broadwater County, the water should be safe to irrigate a garden. However, if you are concerned and want to reduce your risk there are a few things you can do: • Establish raised garden beds with imported soil which would reduce the arsenic concentration in the soil. • Grow fewer root crops. Instead, grow leafy greens and above ground fruits and vegetables. • Install a drip system. This reduce the amount of irrigation water touching the leaves of the plants that you may be eating and should further reduce arsenic levels.
Once again, you will likely see issues with plant growth and yield before the arsenic levels exceed FDA standards. Also, keep in mind that there are lots of factors including such as nutrient deficiencies, pH, water, diseases and more that can affect plant growth.
Additional tests may be needed if you are having issues with plant growth to establish the cause before determining that arsenic is the primarily factor.
Contact MSU Extension in Broadwater County with your gardening questions at (406) 266-9242 or allison. kosto@montana.edu.
