Soil arsenic (As) is an occasional urban legacy contaminant due to its former use in pressure-treated wood and in pesticides. Arsenic contamination is less common than lead contamination in urban soils. All soils contain background levels As at relatively low concentrations due to naturally occurring soil As minerals. Average U.S. background soil As ranges from 140 mg kg-1 As and average around 5 mg kg-1 As. In central Ohio the maximum background As concentration is around 21 mg kg-1, and soils with As concentrations above this are contaminated. Even though As content is elevated, a contaminated soil may or may not pose a risk to human health. When soil As concentrations and exposure are sufficient to pose a health risk, the soil is polluted.
Potential health risks of soil arsenic exposure
Health impacts from long-term (chronic) arsenic exposure include skin lesions, and cancers of the skin, bladder, and lungs. Other health impacts which may be related to chronic arsenic exposure include cardiovascular, kidney, and pulmonary disease and diabetes . Pregnant women, infants, and children are more sensitive to the impacts of arsenic. In the US and worldwide, the primary way for people to be exposed to arsenic is through naturally-contaminated well water.
Exposure to soil As occurs primarily from incidental soil ingestion of dust particles transferred from hands or cleared from the airway. While a majority of urban soils do not have heavy metal concentrations that pose a significant risk to human health, As-polluted soils are occasionally found in cities (especially older and larger cities), former industrial areas, and and rural areas (especially in old orchards).
Gardening in arsenic-contaminated soil
Gardeners face additional exposure to soil As through incidental ingestion of dust while working in the garden, hand-to-mouth transfer, and through consumption of contaminated produce. Plants take up very small amounts of As through their roots and As-contaminated soil sticks to produce surfaces . However, soil with low levels of As contamination can be used without concern. (See Interpretation table).
 Ohio Environmental Protection Agency. 2013. Evaluation of Background Metal Soil Concentrations in Franklin County - Columbus Area,.
 CLU-IN | Contaminants > Arsenic > Occurrence. https://clu-in.org/contaminantfocus/default.focus/sec/arsenic/cat/Occurrence/ (accessed 18 March 2020).-
 World Health Organization. Arsenic. https://www.who.int/news-room/fact-sheets/detail/arsenic (accessed 18 March 2020).
 Defoe, P.P., G.M. Hettiarachchi, C. Benedict, and S. Martin. 2014. Safety of gardening on lead- and arsenic-contaminated urban brownfields. J. Environ. Qual. 43(6): 2064–2078. doi: 10.2134/jeq2014.03.0099.
 McBride, M.B., H.A. Shayler, J.M. Russell-Anelli, H.M. Spliethoff, and L.G. Marquez-Bravo. 2015. Arsenic and Lead Uptake by Vegetable Crops Grown on an Old Orchard Site Amended with Compost. Water Air Soil Pollut 226(8): 265. doi: 10.1007/s11270-015-2529-9.