Hello and thank you for your inquiry. There were a lot of components to the question that you submitted, and I wanted to let you know that I reached out to our Livestock Educator to get specific information about safe levels of arsenic in water for livestock. I have reached out to another colleague to provide the similar information about companion animals. When I get that information, likely tomorrow. For now, I wanted to address using the water for vegetables.

I reached out to our Soil Testing Specialist about vegetables. There are some differences between the states in acceptable arsenic levels in water for watering plants. To be on the safe side you would probably want to go with Oregon's acceptable level of < 100 ppb as being safe to use for watering plants. Here are some resources on this.

Elevated arsenic in both the soil and in irrigation water can lead to contamination of vegetable crops. The level of arsenic in the edible portion of the plant varies by species and can be affected by other factors such as the soil type and soil pH. Elevated arsenic can also lead to stunting of plants. Arsenic was previously used in orchards as an herbicide. Arsenic is also naturally found in soil in some places in MI— you can see maps for Berrien County here: https://www.michigan.gov/egle/about/organization/drinking-water-and-environmental-health/contamination-investigation/water-quality-maps

https://extension.umaine.edu/gardening/2022/01/10/safety-of-watering-with-arsenic-in-well-water/

https://wellwater.oregonstate.edu/sites/wellwater.oregonstate.edu/files/arsenic_in_well_water.pdf

https://www.maine.gov/dhhs/mecdc/environmental-health/eohp/wells/documents/arsenicresultstipsheet.pdf

I will post another response to you once I get the additional information.

Thank you so much for this - it’s really helpful and fascinating. I noted on the Berrien County map that there’s a large red circle that’s basically over our property :) I’m thinking that somehow earlier test results from our previous well made it into a database? In any event, I’m very curious whether in these situations there’s any coordinated effort to let landowners know they may want to have their well water tested? Our new neighbors had no idea this was potentially an issue (they now plan to get their water tested as well).

I look forward to the info on livestock and companion animals! Thanks again.

Hello again, 

Glad you found the information useful. Keep in mind that some arsenic in naturally occurring, and some can be in the soil as arsenic was used as an herbicide in orchards before we realized that wasn't a good idea. So, while there are is no coordinated effort to let people know about arsenic, if you have some idea what occurred on your land in the past, that can provide a clue that you might want to be aware of arsenic and test your water. It is always a good idea, when considering purchasing a home, to check with the local or regional health department to see if there are any known concerns in the area, as they would be familiar with any issues in the area.

Now for the other information that I said I'd provide:

Companion Animals:

I talked with a couple of private practice veterinarians from Family Friends Veterinary Hospital in Grand Rapids (I don’t have any connections to the MSU Small Animal Vet program anymore) and they said that drinking water containing more than 0.25% arsenic is considered toxic for animals, however cats are generally more sensitive than other animals.  I would also advise them to talk with their veterinarian about their water in conjunction with their food; just as in livestock, pet food also contains acceptable levels of arsenic.

Livestock:

Karen Chou, Ph.D., MSU Associate Professor of Environmental Toxicology, provided the following information on Arsenic levels for domestic livestock drinking water. 

As of arsenic concentrations in animal products, existing information does not allow us to estimate the levels of arsenic in the animal products with reasonable confidence, because only a portion of the arsenic in animal products comes from the arsenic in drinking water. The rest comes from the feed.

FDA monitors arsenic concentrations in food items on the market. It is my understanding that the purpose of FDA’s monitoring is to identify whether individuals in a subpopulation, such as infants, children or pregnant women, are exposed to unacceptable levels of arsenic, and to prioritize regulatory actions if any regulatory measures of specific food items are needed.

I think the following information may be useful, too, for understanding the health effects and regulatory decisions.

The two forms of arsenic in human food and animal feed:

Arsenic exists in two forms, either organic or inorganic. The known health effects, cancer or non-cancer, are mostly caused by its inorganic forms, with possible exceptions of methylated arsenic compounds. Arsenic in its organic forms, in general, is much less toxic than the inorganic forms and, therefore, not the targets of institutional regulation. Existing regulatory or recommended levels for arsenic are intended for minimizing the amounts of inorganic forms of arsenic substances in food, feed, and beverages.

NRC maximum tolerable levels for domestic animals:

In general, the higher the amounts of arsenic in feed and drinking water, the higher the amounts of arsenic are likely to be found in the animal products. For the health and production of animals, the National Research Council (NRC) has recommended a maximum drinking water standard of 0.2 mg/L (200 ppb) for agricultural animals, and a maximum tolerable level (MTL) of 30 mg/kg (30,000 ppb) in feed (NRC 2005). Nonetheless, the NRC Committee acknowledges that at the recommended MTL, the concentrations of arsenic in liver and kidney of the animals resulted from the MTL in feed could be unacceptable for human consumption. The Committee did not specify the concentration that is considered as unacceptable.

FDA’s role in arsenic concentrations in food:

The FDA monitors and regulates levels of arsenic in food through several programs, including the Total Diet Study, the Toxic Elements in Food and Foodware, Radionuclides in Food Compliance Program, and through targeted sampling assignments.

In the US, currently, there are three regulatory levels: (1) a maximum contamination level for public water supply (EPA 2001), (2) an action level for infant rice cereal, and (3) a draft action level for apple juice (FDA Website). These regulatory levels are explained further below under its subheadings.

To prioritize future regulatory actions on arsenic in certain food items, FDA has a Closer to Zero action plan, through which the agency will identify actions to reduce exposure to arsenic and other toxic elements from foods eaten by infants and children. The plan focuses on infants and children’s exposure to arsenic because they have been identified to be the vulnerable subpopulations to potential arsenic toxicity in food and beverages. This four-stage plan, started in April of 2021, will establish interim reference levels for certain toxic elements as appropriate. Arsenic is one of elements mentioned in the plan. Visit FDA’s Closer to Zero website to understand how a food item may be selected for future regulatory actions (FDA Website 2021).

Public drinking water supply:

The enforceable maximum contamination level (MCL) in drinking water is set at 0.01mg/L by the US EPA. This regulatory level of MCL at 0.01 mg/L is enforceable, and it is determined based on toxicity assessment, as well as economic and technological feasibilities. Nonetheless, because of the potential health effects at very small amounts of arsenic in water, EPA has a maximum contamination level goal (MCLG) of zero for public water systems under the Safe Drinking Water Act.

Infant rice cereal and apple juice:

US FDA has an action level for inorganic arsenic in rice cereals for infants (0.1 mg/kg) and a draft action level for arsenic in apple juice (0.01 mg/L) (FDA Website). Both action levels are assessed for protecting infant/children’s health. Rice plant tends to absorb much higher amounts of arsenic and accumulates higher concentrations of inorganic arsenic when compared with other grains. As for apple juice, there is also a high tendency for apple juice to contain elevated concentrations of inorganic arsenic. Some of the arsenic in apple juice could come from left over arsenic residues from “old” arsenic-containing pesticides applied previously.

Inorganic arsenic in drinking water for agriculture animals:

NRC Committee on Minerals and Toxic Substances in Diets and Water for Animals defines the maximum tolerable level (MTL) as “a level that when fed for a defined period of time, will not impair animal health or performance (NRC 2005).” The Committee has recommended a MTL of 30 mg/kg in feed and a MTL of 0.2 mg/L (200 ppb) in drinking water for domestic animals.

Arsenic deposited in fatty organs/tissue:

Animals, having the biological functions to transform significant amounts of inorganic arsenic into organic forms, may be viewed as an important detoxification buffer in the food chain, i.e. from the inorganic forms of arsenic in water and plants to the bio-transformed products in its organic forms in the animal products, such as meat, milk, and eggs in human diets.

Arsenic deposited in fatty tissue/organs is mostly in its organic forms, which is less toxic than its inorganic forms. Fat usually contains less than 0.01mg/kg of inorganic arsenic, while vegetable oil contains relatively higher concentrations of inorganic arsenic, ranging from above 0.01 to above 0.02. Nonetheless, excessive amounts of inorganic arsenic in animals’ drinking water and feed may result in excessive high arsenic contents in animal tissue/organs, especially in the liver and kidneys.

What contributes to most of the inorganic arsenic in human diet?

In general, in the western diet, animal products combined, including milk & milk products, meat, and eggs, contribute to rather a small portion of the total inorganic arsenic in adults’ diets, roughly 5%. “Cereals and cereal products” and “water & non-alcoholic beverages” contribute to the greatest amounts of total inorganic arsenic in the diet, a combined portion about 61%, followed by vegetables & fruits, about another subtotal of 18% (Cubadda et al. 2017).

To protect the health of consumers and ensure fair practices in the food trade, the United Nations also provides international standards (maximum level, ML) of inorganic arsenic: 0.1 mg/kg for edible fats and oils (including fish oil), 0.35 mg/kg for husked rice, and 0.2 mg/kg for polished rice (United Nations 2019).

References cited in this communication:

Australian Government. 2021. Australian New Zealand Food Standards Code – Schedule 19 – Maximum levels of contaminants and natural toxicants.

Cubadda, F., B. P. Jackson, K. L. Cottingham, Y. O. Van Horne & M. Kurzius-Spencer (2017) Human exposure to dietary inorganic arsenic and other arsenic species: State of knowledge, gaps and uncertainties. Science of the Total Environment, 579,
1228-1239.

EPA. 2001. Technical fact sheet: Final rule for arsenic in drinking water. ed. O. o. Water. Washington D.C.

FDA Website. Chemical, Metals, Natural Toxins & Pesticides Guidance Documents & Regualtions. Links to FDA guidance about Arsenic in rice cereals for infants, apple juice, and bottled water. ---. 2021. Closer to Zero: action plan for baby foods.

NRC. 2005. Mineral tolerance of animals: Second revised edition. Washington, D. C.: National Academies Press.

United Nations. 2019. Codex Alimentarius, international food standards, General standard for contaminates and toxins in food and feed. ed. F. WHO.

Again, this is super interesting and helpful. One thing tho - how do I translate parts per billion into a percentage? I tried using online calculators and got results that I think I'd have to be a mathematician to interpret :)

Thanks!