Exposure assessment and risk characterization from trace elements following soil ingestion by children exposed to playgrounds, parks and picnic areas

Characteristics of the Atmospheric Pollution and Health Risk of Arsenic and Heavy Metals (Cu,Pb,Cr,Ni,Hg) in PM2.5 during Heating Period in Xining ,China

The human risks of As and heavy metals (Cu, Ni, Cr, Pb, Cd and Hg) in fine particulate matter (PM2.5) in Xining, China is investigated here in this study. Cu, As and Pb are the most abundant elements in stationary monitoring station for atmospheric pollution and mountain Najia. As, Pb and Cr are the most abundant elements in the park of organisms and Xining Special Steel between the studied metals and metalloids in PM2.5. Pb and As showed a higher bio-accessibility. It has been shown that the carcinogenic risks of As, Cd, Cr and Ni in PM2.5 via dermal contact and inhalation exposure are within the acceptable level (<1×10-4) for both children and adults, but there is a potential carcinogenic risk posed by Pb via ingestion. As for non-carcinogenic health risks, the hazard index values for all the studied elements suggested no health risks via ingestion and dermal contact, but a potential one via inhalation of adults. Values of hazard quotient and hazard index indicated the non-carcinogenic risks from the studied metals and metalloids to children via ingestion, dermal contact and inhalation pathways during heating period in Xining given the present air quality .

Effect of weathering product assemblages on Pb bioaccessibility in mine waste: implications for risk management

General assessments of orebody types and associated mine wastes with regard to their environmental signature and human health hazards are needed to help in managing present and historical mine waste facilities. Bioaccessibility tests and mineralogical analysis were carried out on mine waste from a systematic sampling of mine sites from the Central Wales orefield, UK. The bioaccessible Pb widely ranged from 270 to 20,300 mg/kg (mean 7,250 mg/kg, median 4,890 mg/kg), and the bioaccessible fraction from 4.53 to >100% (mean 33.2%, median 32.2%), with significant (p=0.001) differences among the mine sites. This implies sensitivity of bioaccessibility to site-specific conditions and suggests caution in the use of models to assess human health impacts generalised on the basis of the mineral deposit type. Mineralogical similarities of the oxidation products of primary galena provided a better control over the observed Pb bioaccessibility range. The higher Pb bioaccessibility (%) was related to samples containing cerussite, irrespective of the presence of other Pb minerals in the mineral assemblage; lower Pb bioaccessibility resulted where anglesite was the main Pb mineral phase and cerussite was absent. A solubility diagram for the various Pb minerals in the waste was derived using PHREEQC model, and the experimental Pb concentrations, measured in the simulated gastric solution, were compared with the equilibrium modelling results. For samples containing cerussite, the model well predicted the soluble Pb concentrations measured in the gastric solution, indicative of the carbonate mineral phase control on the Pb in solution for these samples and little kinetic control on the dissolution of cerussite. On the contrary, most mine waste samples containing dominant anglesite and or plumbojarosite (no cerussite) had lower solution Pb values, falling at or below the anglesite and plumbojarosite solubility equilibrium concentrations, implying kinetic or textural factors hindering the dissolution.

Exposure assessment and distribution of polychlorinated biphenyls (PCBs) contained in indoor and outdoor dusts and the impacts of particle size and bioaccessibility

The size fraction, bioaccessibility and associated human daily intake of PCBs via indoor and outdoor dust collected from two most populated urban centers of Pearl River Delta (PRD), China, were studied. The ΣPCBs levels (ng g(-1)) in indoor (51.9-264) and outdoor (4.02-228) dust in Guangzhou (GZ) were found higher than those in indoor (17.4-137) and outdoor (7.75-114) dust of Hong Kong (HK). Hexa-PCB was the largest contributor in dust samples (29-64%), followed by tri-PCB. The size fraction of PCBs indicated a high accumulation effect of particles less than 63 μm, while the lowest was found in 280-2000 μm. Toxic equivalency (TEQ) of dioxin-like PCBs in indoor dust of GZ and HK was 2 to 13 times higher than that in outdoor dust. The bioaccessibility of PCBs was determined as 5-61% depending on individual PCB congeners under study and bioaccessible PCB exposure was significantly lower than the estimate for total PCB. The daily intake of bioaccessible PCBs via dust ranged in 0.02-8.95 and 0.37-17.8 ng day(-1) in GZ while 0.01-4.95 and 0.16-9.83 ng day(-1) in HK for adults and children, respectively. Dust ingestion contributed to 0.49-10.6% of overall non-dietary PCB exposure (dust ingestion and inhalation) for adults while 12.9-35% for children, indicating the dominant contribution from inhalation.

Children's exposure to mercury-contaminated soils: exposure assessment and risk characterization

Exposure to mercury (Hg)-contaminated soils may pose a health risk to children by way of oral, dermal, and inhalatory pathways. However, risk characterization studies, including contaminant bioaccessibility with child-specific exposure parameters and scenarios, are lacking. The objectives of this study were (1) to assess children's Hg exposure using characterization and oral bioaccessibility data from Hg-contaminated soils characterized in previous studies (n = 8); and (2) to characterize probabilistic risk in terms of hazard index (HI) considering ingestion, dermal, and inhalation pathways. Total Hg concentrations in soils ranged from 2.61 to 1.15 × 10(4) mg kg(-1). For moderately contaminated soils (S1-S5: Hg ≤ 12.15 mg kg(-1)), low oral bioaccessibility values (1.5-7.5 %) lead to HI < 1 in all scenarios. However, exposure to highly contaminated soils (S6-S8) may pose serious risks to children under normal exposure (HI 0.89-66.5) and soil-pica behaviour scenarios (HI up to 131). All three pathways significantly contributed to the risk. Using total Hg concentrations in calculations (assuming 100 % bioavailability) instead of considering Hg bioavailability leads to risk overestimation. Further research on oral, inhalatory, and dermal bioavailability of Hg, as well as child play behaviour, is recommended to obtain more accurate risk estimates.

Bioaccessibility and health risk assessment of arsenic in arsenic-enriched soils, Central India

Incidental soil ingestion is expected to be a significant exposure route to arsenic for children because of the potentially high arsenic contents found in certain soils. Therefore, it is prudent to get information on oral bioaccessibility of arsenic following incidental soil ingestion and its relevance in health risk assessment for future remediation strategies. Soil samples were collected from eight villages of Ambagarh Chauki block, Chhattisgarh, Central India. The soils from seven villages had total arsenic content more than the background level of 10mgkg(-1) (ranged from 16 to 417mgkg(-1)), whereas the total arsenic content of soil from Hauditola was 7mgkg(-1). Bioaccessible arsenic assessed by the simplified bioaccessibility extraction test (SBET) ranged from 5.7 to 46.3%. Arsenic bioaccessibility was significantly influenced by clay content (R(2)=0.53, p<0.05, n=8), TOC (R(2)=0.50, p<0.05, n=8), Fe content (R(2)=0.47, p<0.05, n=8) and soil pH (R(2)=0.75, p<0.01, n=8). Risk assessment of the study sites showed that hazard index of arsenic under incidental soil ingestion was below 1 in all the study sites, except Kaudikasa. However, carcinogenic risk probability for arsenic to children from the villages Meregaon, Thailitola, Joratarai and Kaudikasa was below acceptable level (<1×10(-4)), suggesting potential health risk for children from these sites could not be overlooked. With high carcinogenic risk value (3.8E-05) and HI index (>1) for arsenic in soils of Kaudikasa, attention should be paid for development of remediation measure.

Importance of the oral arsenic bioaccessibility factor for characterising the risk associated with soil ingestion in a mining-influenced zone

Arsenic is a carcinogenic metalloid and the risks of accidental ingestion should therefore be borne in mind when assessing areas with high levels of this element. In this work, the concentrations of bioaccessible As in mining-influenced soils, in SE Spain are determined. The risk posed by the accidental ingestion is studied in two soil fractions (<2mm and <250μm), taking into consideration the possible uses of the soils (residential/agricultural) and possible receptors (adults and/or children). The properties and mineralogical composition of 26 soil samples are analysed. The results showed that the use of a conservative approach to calculate the Chemical Daily Intake (CDI) based on the total concentrations of arsenic, may overestimate the risk existing in the zone, leading to problems in the management of contaminated soils. The paper emphasises the importance of considering the amount of bioaccessible As in the <250μm fraction before permitting land near temporary watercourses to be used for residential purposes, as beaches or for agriculture.

Comparison of human exposure pathways in an urban brownfield: reduced risk from paving roads

Risk assessments often do not quantify the risk associated with soil inhalation. This pathway generally makes a negligible contribution to the cumulative risk, because soil ingestion is typically the dominant exposure pathway. Conditions in northern or rural centers in Canada characterized by large areas of exposed soil, including unpaved roads, favor the resuspension of soil particles, making soil inhalation a relevant risk pathway. The authors determined and compared human exposure to metals and polycyclic aromatic hydrocarbons (PAHs) from soil ingestion and inhalation and analyzed the carcinogenic and noncarcinogenic risks before and after roads were paved in a northern community. To determine the inhalation exposure, three size fractions of airborne particulate matter were collected (total suspended particulates [TSP], particulate matter with an aerodynamic diameter less than 10 µm [PM10], and particulate matter with an aerodynamic diameter less than 2.5 µm [PM2.5]) before and after roads were paved. Road paving reduced the concentration of many airborne contaminants by 25 to 75%, thus reducing risk. For example, before paving, the carcinogenic risk associated with inhalation of Cr was 3.4 excess cancers per 100,000 people exposed, whereas after paving, this risk was reduced to 1.6 in 100,000. Paving roads reduced the concentrations of total suspended particulates (TSP; p < 0.1) and PM10 (p < 0.05) but not PM25. Consequently, the ingestion of inhaled soil particles was substantially reduced. The authors conclude that resuspended soil is likely an important source of risk for many northern communities and that paving roads is an effective method of reducing risk from the inhalation of soil particles.

Counter-current acid leaching process for copper azole treated wood waste

This study explores the performance of a counter-current leaching process (CCLP) for copper extraction from copper azole treated wood waste for recycling of wood and copper. The leaching process uses three acid leaching steps with 0.1 M H2SO4 at 75degrees C and 15% slurry density followed by three rinses with water. Copper is recovered from the leachate using electrodeposition at 5 amperes (A) for 75 min. Ten counter-current remediation cycles were completed achieving > or = 94% copper extraction from the wood during the 10 cycles; 80-90% of the copper was recovered from the extract solution by electrodeposition. The counter-current leaching process reduced acid consumption by 86% and effluent discharge volume was 12 times lower compared with the same process without use of counter-current leaching. However, the reuse of leachates from one leaching step to another released dissolved organic carbon and caused its build-up in the early cycles.

Concentrations and seasonal variations of polybrominated diphenyl ethers (PBDEs) in in- and out-house dust and human daily intake via dust ingestion corrected with bioaccessibility of PBDEs

The objective of this study was to investigate the concentrations, seasonal variations, bioaccessibility, and associated human daily intake of polybrominated diphenyl ethers (PBDEs) in in- and out-house dust collected in Shanghai, China. The PBDE concentrations varied from 131.6 to 3,886.7 ng g(-1) (with an average of 948.2 ng g(-1)) in in-house dust and from 8.7 to 3,116.3 ng g(-1) (with an average of 290.8 ng g(-1)) in out-house dust during four seasons. The PBDE concentrations in the autumn were the lowest for both in- and out-house dust. Among the detected PBDEs, BDE209 was the predominant congener, accounting for more than 80% of the total PBDE amounts. The bioaccessibility of PBDEs, measured using a simulation system of human gastrointestinal tract, was determined as 14.2-66.4% depending on individual PBDE congeners and showed significant negative correlations with organic matter in dust. After corrected with the bioaccessibility of PBDEs, the human daily intake of PBDEs via dust ingestion was calculated to be 0.4-21.4 and 4.3-40.6 ng day(-1) for an average adult and child in Shanghai, respectively. The values were much lower than most estimates in the literature, in which the bioaccessibility of PBDEs were not taken into account, suggesting that the intake of PBDEs may have been overestimated.

Phytoremediation of soil contaminated with cadmium, copper and polychlorinated biphenyls

A pot experiment and afield trial were conducted to study the remediation of an aged field soil contaminated with cadmium, copper and polychlorinated biphenyls (PCBs) (7.67 +/- 0.51 mg kg(-1) Cd, 369 +/- 1 mg kg(-1) Cu in pot experiment; 8.46 +/- 0.31 mg kg(-1) Cd, 468 +/- 7 mg kg(-1) Cu, 323 +/- 12 microg kg(-1) PCBs for field experiment) under different cropping patterns. In the pot experiment Sedum plumbizincicola showed pronounced Cd phytoextraction. After two periods (14 months) of cropping the Cd removal rates in these two treatments were 52.2 +/- 12.0 and 56.1 +/- 9.1%, respectively. Total soil PCBs in unplanted control pots decreased from 323 +/- 11 to 49.3 +/- 6.6 microg kg(-1), but with no significant difference between treatments. The field microcosm experiment intercropping of three plant species reduced the yield of S. plumbizincicola, with a consequent decrease in soil Cd removal. S. plumbizincicola intercropped with E. splendens had the highest shoot Cd uptake (18.5 +/- 1.8 mg pot(-1)) after 6 months planting followed by intercropping with M. sativa (15.9 +/- 1.9 mg pot(-1)). Liming with S. plumbizincicola intercropped with M. sativa significantly promoted soil PCB degradation by 25.2%. Thus, adjustment of soil pH to 5.56 combined with intercropping with S. plumbizincicola and M. sativagave high removal rates of Cd, Cu, and PCBs.

Incorporating bioaccessibility into human health risk assessments of heavy metals in urban park soils

Contaminants in urban soils can directly pose significant human health risks through oral ingestion, particle inhalation, and dermal contact, especially for children in public parks. Both non-carcinogenic and carcinogenic risks of heavy metals (Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn) were characterized in 40 surface soils (exposed lawns) from 14 urban parks in Xiamen, China. Results based on total metal concentrations may overestimate the actual risks in comparison with oral bioaccessibility assessment that were estimated by a simplified physiologically based extraction test (SBET). After considering the soil-specific bioaccessibility (Cd>Cu>Pb>Mn>Zn>Co~Ni>Cr), the non-cancer hazard of Pb to children via oral ingestion should be a consideration though its Hazard Index (HI) was below one. The overall cancer risks to adults still exceeded the target value 10(-6), mainly contributed by Cr (93.8%) and Pb (6.19%) via dermal contact (68.3%) and oral ingestion (30.4%). To produce a more realistic estimation for human health risks of metal contamination in urban soils, a framework combining land use type and bioaccessibility is recommended and thereby should be applied for the derivation of risk-based, site-specific soil guidelines.

Health risk assessment of lead ingestion exposure by particle sizes in crumb rubber on artificial turf considering bioavailability

OBJECTIVES

The purpose of this study was to assess the risk of ingestion exposure of lead by particle sizes of crumb rubber in artificial turf filling material with consideration of bioavailability.

METHODS

This study estimated the ingestion exposure by particle sizes (more than 250 um or less than 250 um) focusing on recyclable ethylene propylene diene monomer crumb rubber being used as artificial turf filling. Analysis on crumb rubber was conducted using body ingestion exposure estimate method in which total content test method, acid extraction method and digestion extraction method are reflected. Bioavailability which is a calibrating factor was reflected in ingestion exposure estimate method and applied in exposure assessment and risk assessment. Two methods using acid extraction and digestion extraction concentration were compared and evaluated.

RESULTS

As a result of the ingestion exposure of crumb rubber material, the average lead exposure amount to the digestion extraction result among crumb rubber was calculated to be 1.56×10(-4) mg/kg-day for low grade elementary school students and 4.87×10(-5) mg/kg-day for middle and high school students in 250 um or less particle size, and that to the acid extraction result was higher than the digestion extraction result. Results of digestion extraction and acid extraction showed that the hazard quotient was estimated by about over 2 times more in particle size of lower than 250 um than in higher than 250 um. There was a case of an elementary school student in which the hazard quotient exceeded 0.1.

CONCLUSIONS

Results of this study confirm that the exposure of lead ingestion and risk level increases as the particle size of crumb rubber gets smaller.

Bioaccessibility and health risk of arsenic, mercury and other metals in urban street dusts from a mega-city, Nanjing, China

The oral bioaccessibility and the human health risks of As, Hg and other metals (Cu, Pb, Zn, Ni, Co, Cd, Cr, Mn, V and Fe) in urban street dusts from different land use districts in Nanjing (a mega-city), China were investigated. Both the total contents and the oral bioaccessibility estimated by the Simple Bioaccessibility Extraction Test (SBET) of the studied elements varied with street dusts from different land use districts. Cd, Zn, Mn, Pb, Hg and As showed high bioaccessibility. SBET-extractable contents of elements were significantly correlated with their total contents and the dust properties (pH, organic matter contents). The carcinogenic risk probability for As and Cr to children and adults were under the acceptable level (<1×10(-4)). Hazard Quotient values for single elements and Hazard Index values for all studied elements suggested potential non-carcinogenic health risk to children, but not to adults.