Assessment of source-oriented health risk associated with the oral ingestion of heavy metals in dust within an iron/steel smelting-affected area of the North China Plain.

Heavy metals (HMs) from iron/steel smelting activities pose notable risks to human health, especially to those living around industrial facilities of North China Plain, the base of China's steel production. In this study, 78 outdoor windowsill dust samples were collected around a large-scale iron/steel smelter with more than 65 years of production history in the western North China Plain. Nine HMs were analysed to comprehensively assess the health risks by integrating Monte Carlo simulation, oral bioaccessibility, and source apportionment. Results showed serious pollution with Cd, Pb, and Zn based on their geo-accumulation index values and concentrations. Four potential sources including industrial sources (49.85%), traffic sources (21.78%), natural sources (20.58%), and coal combustion (7.79%) were quantitatively identified by multivariate statistical analysis. The oral bioaccessibilities of HMs determined by the physiologically based extraction test ranged from 0.02% to 65.16%. Zn, Mn, Cd, and Pb had higher bioaccessibilities than other HMs. After incorporating oral bioavailability adjustments, noncarcinogenic and carcinogenic risks were significantly reduced, especially for adults. The mean hazard index (HI) for children and adults was below the safety threshold (1.0), whereas the mean of the total carcinogenic risk (TCR) based on HM bioaccessibilities in the gastric phase remained above the acceptable level (1.0E-06) (children: 5.20E-06; adults: 1.16E-06). Traffic sources warranted increased concern as it substantially increased TCR. Cd was identified as the priority pollution in iron/steel smelting areas. Assessing source-oriented health risks associated with oral ingestion exposure can guide the management and control of HM contamination within iron/steel smelting-affected areas.

Health risk assessment of heavy metals in road dust from the fourth-tier industrial city in central China based on Monte Carlo simulation and bioaccessibility.

Health risks caused by heavy metal (HM) exposure in road dust has attracted extensive attention, but few studies have focused on the health risks of residents living in small- and medium-sized cities with rapid industrialization and urbanization. Thus, 140 road dust samples were collected across Anyang, a typical fourth-tier industrial city in central China, which were analysed for 10 different HMs (Mn, Zn, Pb, V, Cr, As, Cd, Ni, Cu and Co). Monte Carlo simulation and bioaccessibility were used to quantify the health risks of heavy metals comprehensively in road dust. Results revealed a remarkable accumulation of Mn, Zn, Pb, Cd and Cu. According to the Geo-accumulation index and potential ecological risk index, Cd was priority control pollutant. Moreover, 55.0% of the road dust samples reached heavily polluted level, and 52.86% of the samples were at high ecological risk levels. These results illustrated that HM contamination was serious and universal in the road dust of Anyang. The occurrences of HMs were allocated to traffic emissions, natural sources, industrial activities and agricultural activities with contribution rates of 35.4%, 6.0%, 41.6% and 17.0%, respectively. Except for Zn in the gastric phase, all other HMs had relatively low bioaccessibilities in the gastrointestinal system, usually less than 20%. The bioaccessibilities of most HMs were higher in the gastric phase, except for Cr, Ni and Cu, which remained higher in the intestinal phase. The non-carcinogenic risk and carcinogenic risk were remarkably reduced when considering the HM bioaccessibilities in the gastrointestinal system, especially for adults. The outcomes of this paper are valuable for understanding HM contamination in road dust and highlight the importance of risk assessment for populations living in the fourth- and fifth-tier cities.

Multi-pathway mercury health risk assessment, categorization and prioritization in an abandoned mercury mining area: A pilot study for implementation of the Minamata Convention.

This is a systematic study of human health risk assessment (HHRA) and risk categorization for inorganic mercury (IHg) and methylmercury (MeHg) in Hg mining areas. A multi-pathway exposure model coupled with Monte Carlo simulation was constructed for the Wanshan Hg mining area (WSMM), Southwestern China, with consideration of oral ingestion (foodstuffs, water and soil), dermal contact (water and soil), and inhalation (gaseous Hg and particulate Hg). The results show that dietary intake (food and water), gaseous Hg inhalation, oral ingestion of soil particles, dermal contact, and particulate Hg inhalation comprised 88.3-96.3%, 3.49-6.14%, 0.14-5.3%, 0.02%, and <0.01% of total IHg ingestion, respectively. As expected, rice consumption contributed the highest proportion (86.3-92.7%) of MeHg. The study shows that the elevated MeHg exposure risk is the most significant issue in Hg mining areas. In addition, Hg risk categorization and prioritization in the WSMM are established for the first time based on rice-based exposure doses of IHg and MeHg. Target areas for future treatment and/or remediation are characterized according to thresholds of reference dose and provisional tolerable weekly intake for exposure doses, as well as risk screening values and risk control values for contaminated soil. The proposed multi-pathway exposure model is strongly recommended for the HHRA of Hg-contaminated sites worldwide and helps facilitate the implementation of the Minamata Convention on Mercury.

Dietary exposure assessment of cadmium, arsenic, and lead in market rice from Sri Lanka.

Rice is frequently reported to be contaminated with heavy metals (HMs); thus, the human health risks from its consumption have received increasing attention. A total of 165 commercial rice samples from Sri Lanka were collected to determine their cadmium (Cd), arsenic (As), and lead (Pb) concentrations. The exposure risk for Sri Lankans from the estimated daily intakes (EDIs) of these toxicants was assessed. Simultaneously, non-carcinogenic and carcinogenic risks were evaluated using hazard quotients (HQs) and the hazard index (HI). The results revealed that the average levels of Cd, As, and Pb in commercial rice were 0.080 ± 0.130, 0.077 ± 0.040, and 0.031 ± 0.050 mg/kg, respectively, with ranges of 0.003-0.727, 0.019-0.217, and 0.001-0.345 mg/kg (expressed on a dry weight basis), respectively. The average EDIs of Cd, inorganic As (iAs), and Pb were 0.772, 0.490, and 0.306 µg/kg body weight (bw)/day, respectively; these were below provisional tolerable weekly intake (PTWI) values recommended by the Joint FAO/WHO Expert Committee on Food Additives (JECFA), but iAs was above the recommended reference doses (RfDs) recommended by the United States Environmental Protection Agency (USEPA). However, approximately 25% and 75% of the Cd and iAs HQs for the Sri Lankan population, respectively, were greater than 1, suggesting a potential health risk, whereas the HQs for Pb was less than 1. Considering the additive effect, HI values of the P90, P95, P97.5, and P99 percentiles would reach 4.773, 6.458, 8.392, and 11.614, implying that intake of the combined metals might result in potential health risks.

Dietary exposure assessment of total mercury and methylmercury in commercial rice in Sri Lanka.

Methylmercury (MeHg) in rice has attracted growing health concern over the past decade, due to the accumulation of high MeHg levels, which may pose potential health risk to humans. Rice is the staple food in Sri Lanka; nevertheless, the presence of micro pollutants, such as MeHg has been not investigated. Therefore, commercial rice samples from the Sri Lankan market (n = 163) were measured to reveal the total mercury (THg) and MeHg levels. THg (mean: 1.73 ±â€¯0.89 ng/g, range: 0.21-6.13 ng/g) and MeHg concentrations (mean: 0.51 ±â€¯0.37 ng/g; range: 0.03-3.81 ng/g) were low. Compared to the fish MeHg exposure, the rice MeHg exposure was generally lower in different consumption groups, suggesting that rice plays a less role than fish in MeHg exposure in Sri Lanka. Babies (infants and toddlers) at one year old may face fish MeHg exposure (0.17 µg/kg bw/day) higher than the reference dose for MeHg (RfD)-0.1 µg/kg bw/day, which was more than 5 times that of rice MeHg exposure (0.031 µg/kg bw/day). Future studies in Sri Lanka should focus on health impacts under long-term overexposure of MeHg, especially in vulnerable populations. Some diet changes should be made to mitigate MeHg exposure levels in Sri Lankans.

Weir building: A potential cost-effective method for reducing mercury leaching from abandoned mining tailings.

To mitigate mercury (Hg) pollution and reduce Hg downstream transportation, a weir was designed by a river system that had been inflicted by leachate from the slagheap of the Yanwuping Hg mine in Wanshan Hg mining area. A whole year monitoring of Hg species was conducted, and the efficiency of Hg reduction by the weir application was evaluated. The Hg concentrations in the river water were significantly higher in the wet season than in the dry season. Waterflow was confirmed to be the main driving factor for Hg mobilization and transportation, and an episode study revealed that most Hg was released in times of storms. Increased monitoring and preventive maintenance measures need to be taken on barriers in advance of storms. A large proportion of the total Hg (THg) and methylmercury (MeHg) is associated to particles. During the study period, approximately 412 g THg and 4.04 g total MeHg (TMeHg) were released from the YMM slagheap, of which 167 g THg and 1.15 g TMeHg were retained by the weir. Annually, 40.4% THg and 38.4% TMeHg was retained by the weir. Weir construction is considered as a potential cost-effective measure to mitigate Hg in river water and should be promoted and extended in the future after optimization.