Potential human inhalation exposure to soil contaminants in urban gardening on brownfields sites: A breath of fresh air?

Authors: WEEKS, JOSEPH - Kansas State University; HETTIARACHCHI, GANGA - Kansas State University; SANTOS, EDUARDO - Kansas State University; Tatarko, John

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/15/2021
Publication Date: 4/14/2021
Publication URL: https://handle.nal.usda.gov/10113/7709435
Citation: Weeks, J.J., Hettiarachchi, G.M., Santos, E., Tatarko, J. 2021. Potential human inhalation exposure to soil contaminants in urban gardening on brownfields sites: A breath of fresh air?. Journal of Environmental Quality. 50(3):782-790. https://doi.org/10.1002/jeq2.20208.
DOI: https://doi.org/10.1002/jeq2.20208

Interpretive Summary: Urban gardening has experienced increased popularity around the United States. Initially, growers were unaware of potential soil contamination from both organic compounds and trace elements, but due to the efforts of the scientific community, light has been shed on these seemingly “invisible” issues. Three paths of exposure to the human body are typically given for these contaminants: eating contaminated soil (mostly by children), eating produce contaminated with a hazardous substance, and inhalation of soil dust. The first two ways have received much attention; however inhalation has not been fully studied due to the assumption that is the least significant. Two inhalation risk studies were carried out in urban gardens located in Kansas City, Missouri (KCMO) by collecting dust while 269 square foot areas were rototilled. Climate variables were monitored and total inhalable dust amounts were determined using a personal sampling device including a small pump and air filter. For Study 1, soil lead concentration was measured. Particle sizes of the dust collected were estimated through analysis of microscope images of filters. Little dust was collected at either site. Most particles captured however, appeared to be less than 0.00016 inches in diameter suggesting that what was generated could enter deep into the human respiratory system. The amount of dust emitted was correlated with soil moisture to depths of 0.79 to 3.94 inches and 3.94 to 7.87 inches. Rototilling reduced soil clod size and blended lead concentrations, resulting in a more homogeneous distribution of the element. Dust inhalation while tilling is likely not a major lead exposure risk for gardeners but given the high portion of very small particles in what was captured, care should be taken to prevent dust from entering the lubngs as much as possible.

Technical Abstract: Urban gardening has been experiencing increased popularity around the United States. Initially, growers were unaware of potential soil contamination from both organic compounds and trace elements, but due to the efforts of the scientific community, light has been shed on these seemingly “invisible” issues. Three pathways of exposure to the human body are typically cited for these contaminants: ingestion of soil directly, consumption of produce containing or superficially contaminated with a hazardous substance and inhalation of soil dust. The first two modes have received much attention; however the contribution of the inhalation route has not been adequately investigated due to the assumption that the pathway is the least significant. Two inhalation risk studies were carried out in urban gardens located in Kansas City, Missouri (KCMO) by collecting dust while 5 m x 5 m plots were rototilled. Microclimatic variables were monitored and total inhalable dust mass was determined using a personal sampling train including a small pump and air filter. For Study 1, soil lead (Pb) concentration was assessed via acid digestion with subsequent analysis using ICP-OES. Particle size distribution of collected particles was estimated through analysis of scanning electron microscope (SEM) images of filters. Little dust was collected at either site. Most particles captured, however, appeared to be less than 4 µm in diameter suggesting that what was generated could enter deep into the human respiratory system. The amount of dust emitted appeared to be correlated with soil moisture in the 2-10 cm and 10-20 cm portion of the soil profile. Tilling reduced soil aggregate size and blended lead concentrations resulting in a more homogeneous distribution of the element. Dust inhalation while tilling is likely not a major lead exposure risk for gardeners but given the preponderance of very small particles in what was captured, care should be taken to prevent dust from entering the respiratory system as much as possible.