Dosimetric Comparison of Exposure Pathways to Human Organs and Tissues in Radon Therapy

Three therapeutic applications are presently prescribed in the radon spas in Gastein, Austria: exposure to radon in a thermal bath, exposure to radon vapor in an exposure chamber (vapor bath), and exposure to radon in the thermal gallery, a former mine. The radiological exposure pathways to human organs and tissues in these therapeutic radon applications are inhalation of radon and radon progeny via the lungs, radon transfer from water or air through the skin, and radon-progeny deposition on the skin in water or air. The objectives of the present study were to calculate radon and radon-progeny doses for selected organs and tissues for the different exposure pathways and therapeutic applications. Doses incurred in red bone marrow, liver, kidneys, and Langerhans cells in the skin may be correlated with potential therapeutic benefits, while doses to the lungs and the basal cells of the skin indicate potential carcinogenic effects. The highest organ doses among the three therapeutic applications were produced in the thermal gallery by radon progeny via inhalation, with lung doses of 5.0 mSv, and attachment to the skin, with skin doses of 4.4 mSv, while the radon contribution was less significant. For comparison, the primary exposure pathways in the thermal bath are the radon uptake through the skin, with lung doses of 334 μSv, and the radon-progeny attachment to the skin, with skin doses of 216 μSv, while the inhalation route can safely be neglected.

Exploring airshed and watershed exposure pathways as mediators of the association between proximity to surface mining and adverse birth outcomes in Central Appalachia

Background Previous work has determined an association between proximity to active surface mining in coal producing counties within Central Appalachia and an increased risk of preterm birth (PTB) and low birthweight (LBW); however, the relative importance of specific exposure pathways explaining this association remains poorly understood. Multiple potential exposure pathways to surface mining activities exist during gestation, including inhalation of particulate matter (airshed exposure), or via exposure to impacted surface waters (watershed exposure). Here, we perform a mediation analysis to explore these pathways and the odds of adverse birth outcomes. Methods We obtained birth records acquired through health departments in WV, KY, VA and TN between 1990 and 2015. Surface mine extents for each year were identified through remotely sensed Landsat imagery. Corresponding airsheds were estimated using the HYSPLIT4 atmospheric trajectory model, while watersheds were assigned using United States Geological Survey’s Watershed Boundary Dataset boundaries. We performed logistic regression to determine associations between exposure and the odds of preterm birth, low birthweight, and term low birthweight, and iteratively included within our models: a) the percent of active surface mining landcover within a 5 km buffer of maternal residence; b) the cumulative potential exposure to air pollutants via the airshed experienced at the maternal residence, and; c) the percent of land experiencing surface mining within the watershed of residency. Results Our baseline models found that active surface mining was associated with an increased odds of PTB (1.09, 1.05 – 1.13) and LBW (1.06, 1.02 – 1.11), while controlling for significant predictors. When mediators were added to the base model, the association between active mining and birth outcomes was reduced (PTB: 1.04, 0.99 – 1.09; LBW 1.04, 0.99 – 1.10), while the odds of PTB and LBW increased with airshed exposure (PTB: 1.14, 1.11 – 1.18; LBW: 1.06, 1.03 – 1.10). Conclusions Results were consistent with a hypothesis of mediation via airshed, but suggested mediation via watershed was less likely. These results suggest that air pollution resulting from surface mining activities may be the primary exposure pathway explaining the association between maternal residence proximity to active surface mining and PTB and LBW.

Bioaccessibilities and health risk assessment of heavy metals in dust from the Guizhou-Guiyang urban zone, China

To investigate the health risks of heavy metals in dust entering the human body from different exposure pathways. In this study, the old urban area of Guiyang was used as the study area to understand the heavy metals concentrations in surface dust, including recreational plazas, main streets, hospitals, residential areas, and schools in this city, and the bioaccessibility in the simulated lung phase and simulated gastrointestinal phase. The results showed that the concentrations of Cu, Pb, Zn, Cd, Ni, and Cr in the dust were higher than the background values, especially the Zn content exceeded the background value by 9.71 times. The bioaccessibility results indicated that the most soluble heavy metals in the simulated lung phase, simulated gastric phase, and simulated intestinal phase were Zn, Ni, and Cu, respectively, and the bioaccessibility of most heavy metals was significantly higher in the gastric phase than in the intestinal phase, and only Cu was higher in the intestinal phase than in the gastric phase. The linear results fit suggested that the total amount of heavy metals alone could not predict the human intake of heavy metals in the dust. Human health risk assessment based on bioaccessibility showed that children had higher non-carcinogenic and carcinogenic risks than adults for both hand-to-mouth ingestion and respiratory inhalation exposure pathways, but none of them exceeded the limit values.

Children Health Risk Assessment of Metals in Total Suspended Particulate Matter (TSP) and PM1 in Kindergartens during Winter and Spring Seasons

This study evaluates the health risks related to heavy metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Se, Zn, and metalloid As) in the indoor dust samples of total suspended particles (TSP) and particles with diameter < 1 μm (PM1). The samples were collected during 5-day periods during the spring and winter seasons in the Upper Silesia region, Poland. The highest concentration among determined trace elements revealed Fe. The greatest concern expressed the concentration of carcinogenic Cd in PM1 (from 6.7 to 9.7 ng/m3), exceeding the permissible value 5 ng/m3 (for PM10). The carcinogenic and non-carcinogenic health risks were assessed for three exposure pathways (inhalation, ingestion, and dermal contact) for preschool children. None of the single trace elements obtained the Hazard Quotient Index (HQ > 1) or carcinogenic risks above the upper acceptable limit (1 × 10−4). However, the cumulative HQ values (SHQ) for three exposure pathways were greater than the safe level. The highest cumulative non-carcinogenic risk presented the TSP in rural kindergartens (2.0 × 10−4). In the same location as the TSP, the highest carcinogenic risk was also observed (9.1 × 10−4). High carcinogenic risks (>10−4) were found for the ingestion pathway of TSP inside urban and rural kindergartens and of PM1 in urban ones. A comparative evaluation shows that the health risks of trace elements in airborne particles in Polish kindergartens bring high risk.

Human Health Risk Assessment of Crude Oil Polluted Soil, Surface & Groundwater Sources in Emohua, Rivers State, Nigeria

This study was carried out to assess the human health risk associated with a crude oil spill site in Emohua Local Government Area of Rivers State, Niger Delta. The Total Content and Fraction’s approaches were adopted to assess the human health risk. Total Content approach was carried out by comparing the concentration of various contaminants in the environmental media studied with the Intervention Values prescribed while the Fractions approach was carried out using RBCA Toolkit for Chemical Releases version 2.6. The results indicate that concentration indices for Total Petroleum Hydrocarbon (TPH) and Polycyclic Aromatic Hydrocarbon (PAH) were greater than the acceptable limit of 1.0 for both the maximum and mean concentrations in soil and groundwater, indicating unacceptable risk at this site. The result from the Fraction’s approach showed that carcinogenic risks are identified for the site through the soil and grounwater exposure pathways as the Total Risk Values for soil (1.7 x10-3) and groundwater (5.6 x 10-1) are higher than the target risk of 1.0 x 10-5 while toxic effects risks are identified for all pathways in the site with Total Health Risk Index for all four pathways greater than the applicable limit of 1.0. Ingestion of groundwater for carcinogenic risk with risk value 5.6 x 10-1 and inhalation of indoor air for non-carcinogenic risk Health Risk Index of 1.0 x104 are identified as the major contributing exposure pathways at this study site. It was therefore concluded that the study site poses unacceptable risk to human health and needs immediate intervention.

Human Health Assessment of Sixteen Priority Polycyclic Aromatic Hydrocarbons in Contaminated Soils of Northwestern Algeria

Background. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental organic contaminants generated by incomplete combustion of organic materials that are widely distributed in soils. Objectives. This study represents the first attempt to examine the health toxicity of 16 detected PAHs in contaminated soil, via different exposure pathways to populations in northwestern Algeria. Methods. The toxicity equivalency quotients (TEQ) of PAHs were evaluated. The carcinogenic risk assessment of incremental lifetime cancer risk (ILCR) from ingestion, inhalation, and dermal exposure pathways to each PAH in soil are described. Results. Incremental lifetime cancer risk values were in the upper limit of the tolerable range (10−6–10−4) for adults and children. The total cancer risk of PAH-contaminated soils for children, adolescents and adults was 2.48×10−5, 2.04×10−5 and 3.12×10−5mg.kg−1d−1, respectively. The highest potential cancer risks were identified for adults and children, with adolescents having the lowest risks. Across exposure pathways, the dermal contact and ingestion pathways had the greatest contributions to the carcinogenic risk of human exposure to PAHs. Conclusions. Further research and guidelines are needed for risk assessments of PAHs in agricultural, residential/urban, and industrial areas, and further risk assessments should include risks posed by exposure through air. Competing Interests. The authors declare no competing financial interests.