Assessment of Potential Human Inhalation Exposure to Soil Trace Elements Resulting from Agricultural Activity on Urban Brownfield Sites.

Urban gardening has been experiencing increasing popularity around the United States for a number of years now spurring a flush of research, not only investigating the best growing techniques, but also exploring areas of potential human health concern. Initially, many growers were unaware of the possibilities of soil contamination with both organic compounds and trace elements. Thankfully, due to the diligent efforts of the scientific community, light has been shed on these seemingly “invisible” issues. Three pathways of exposure are typically cited for soil-borne contaminants to enter the human body: ingestion of soil directly, consumption of produce containing contaminants or superficially contaminated with soil, and inhalation of soil dust. The first two modes have received much attention in recent years, however the contribution of the inhalation route to raising the human body toxin burden has not been adequately investigated. A personal sampling train was utilized to quantify the amount of soil dust one could reasonably expect to respire when in close proximity to a garden site. The device was worn while gardening activity took place (e.g. rototilling) allowing for samples to become entrained on porous PTFE disc filters. Microclimatic variables were monitored and total inhalable dust was determined gravimetrically. Elemental composition was assessed via acid digestion with subsequent analysis using a graphite furnace, and high-resolution scanning electron microscopy- energy dispersive X-ray analysis was used to characterize the dust particles. Data collected at the Washington Wheatley Community Garden located in Kansas City, MO suggest that the inhalation exposure pathway may only be a minor avenue for soil-bound contaminants to enter the body. Soil water content appears to exhibit the greatest influence on the amount of dust generated by soil tillage.