Major Exposure Pathway Research Articles

Harmful Health Impacts of Heavy Metals and Behavioral Changes in Humans

Heavy metal pollution not only affects the environment but also the behavior of people who are greatly dependent on their surrounding environment for their survival. There are both natural and anthropogenic sources of heavy metals but their pollution by manmade activities are quite faster than natural sources. A person gets exposed to heavy metals by four major exposure pathways i.e. inhalation, ingestion, dermal exposure and injection. After exposure to heavy metals, internal normal body functions of an individual gets disturbed. This in turn alters the human behavior from normal to an abnormal state. Various behavioral changes are associated with heavy metals exposure such as depression, anxiety, irregular heartbeats, stress, decrease in strength and power, lack of confidence, restlessness, lack of tolerance and aggressions among the individuals and the society as a whole. This review entails the information regarding sources of heavy metals, exposure pathways and health effects of heavy metals resulting in behavioral changes in humans.

A sensitive method for the determination of per- and polyfluoroalkyl substances in food and food contact material using high-performance liquid chromatography coupled with tandem mass spectrometry

Dietary intake is the major pathway of human exposure to per- and polyfluoroalkyl substances (PFAS). Due to their generally very low concentrations in food, especially for foods of plant origin, and their toxicological relevance, demand is growing for improved selective and sensitive analytical methods for the determination of PFAS in the lower ng/kg range. The relevance is pointed out due to the fact that the European Commission has published limits of quantification (LOQs) in the lower ng/kg range for different food matrices in Recommendation (EU) 2022/1431 on the monitoring of perfluoroalkyl substances in food. For example, LOQs of 2 ng/kg for perfluorooctanesulfonic acid (PFOS), 1 ng/kg for perfluorooctanoic acid (PFOA), 1 ng/kg for perfluorononanoic acid (PFNA) and 4 ng/kg for perfluorohexanesulfonic acid (PFHxS) in fruit, vegetables and baby foods are required. A new, very sensitive method is presented here for the determination of 22 PFAS in food and food contact materials. The method is based on liquid-solid extraction and automated clean-up using two solid phase extraction techniques. The analytes are separated and detected by HPLC-MS/MS. A limit of detection (LOD) of 0.33 ng/kg and an LOQ of 1.0 ng/kg are attained for plant foods such as fruits and vegetables as well as for milk and baby food. For foods of animal origin such as egg, meat, fish and paper-based food contact materials an LOD of 1.6 ng/kg as well as an LOQ of 5.0 ng/kg are attained. PFOS and PFOA were the most abundant compounds in the food samples with concentration as high as 1,051 ng/kg of PFOA in sea weed samples and 772 ng/kg of PFOS in eggs samples. In food contact material samples, higher levels were found with a maximum of 310,000 ng/kg PFHxA. In sum the presented method firstly allows determination of PFAS in a wide variety of foodstuffs and paper-based food contact materials at EU-required concentration ranges.

Laboratory and In situ Selenium Bioaccumulation Assessment in the Benthic Macroinvertebrates Hyalella azteca and Chironomus dilutus.

Selenium (Se) bioaccumulation and toxicity in aquatic vertebrates have been thoroughly investigated. Limited information is available on Se bioaccumulation at the base of aquatic food webs. In this study, we evaluated Se bioaccumulation in two benthic macroinvertebrates (BMI), Hyalella azteca and Chironomus dilutus raised in the laboratory and caged in-situ to a Canadian boreal lake e (i.e., McClean Lake) that receives continuous low-level inputs of Se (< 1μg/L) from a uranium mill. Additional Se bioaccumulation assays were conducted in the laboratory with these BMI to (i) confirm field results, (ii) compare Se bioaccumulation in lab-read and native H. azteca populations and (iii) identify the major Se exposure pathway (surface water, top 1cm and top 2-3cm sediment layers) leading to Se bioaccumulation in H. azteca. Field and laboratory studies indicated overall comparable Se bioaccumulation and trophic transfer factors (TTFs) in co-exposed H. azteca (whole-body Se 0.9-3.1µg/g d.w; TTFs 0.6-6.3) and C. dilutus (whole-body Se at 0.7-3.2µg Se/g d.w.; TTFs 0.7-3.4). Native and lab-reared H. azteca populations exposed to sediment and periphyton from McClean Lake exhibited similar Se uptake and bioaccumulation (NLR, p = 0.003; 4.1 ± 0.8µg Se/g d.w), demonstrating that lab-reared organisms are good surrogates to assess on-site Se bioaccumulation potential. The greater Se concentrations in H. azteca exposed to the top 1-3cm sediment layer relative to waterborne exposure, corroborates the importance of the sediment-detrital pathway leading to greater Se bioaccumulation potential to higher trophic levels via BMI.

Occurrence differences of hexachlorobutadiene and chlorobenzenes in road dust and roadside soil media in an industrial and residential mixed area in Eastern China

The road dust and roadside soil can act as both sinks and sources of hexachlorobutadiene (HCBD) and chlorobenzenes (CBzs), but comparative research on these two adjacent media is extremely limited. In this study, HCBD and CBzs were simultaneously analyzed in road dust and roadside soil samples from an area containing both industrial factories and residential communities in Eastern China. The road dust there was found to have 2–6 times higher contents of HCBD (mean 1.14 ng/g, maximum 6.44 ng/g) and ∑Cl3-Cl6CBzs (22.8 ng/g, 90.6 ng/g) than those in the roadside soil. The spatial distributions of HCBD and CBzs in road dusts were affected by various types of sources, showing no significant discrepancy among the sites. On the contrast, HCBD and CBzs contamination in roadside soils occurring near several factories were strongly correlated to their industrial point sources. Risk assessments showed, at current contamination levels in the road dust and roadside soil, HCBD and CBzs are not likely to induce carcinogenic or non-carcinogenic risks to residents in the studied area. Nevertheless, road dust ingestion, as the major exposure pathway of HCBD and CBzs, should be avoided to reduce the exposure risk. These findings based on the contamination differences between two media provide a new perspective and evidence for screening important sources and exposure pathway of HCBD and CBzs, which would be helpful to their source identification and risk control.

Heavy metals pollution of soil in central plains urban agglomeration (CPUA), China: human health risk assessment based on Monte Carlo simulation.

The present study conducted the concentration evaluation, pollution assessment, source analysis, and risk assessment of heavy metals in the soil of the CPUA, China, to contribute to the smooth construction of urban agglomeration. Elevated levels of mean concentrations of cadmium (Cd), chromium (Cr), and copper (Cu) in the soils were shown compared to background values. Cu and zinc (Zn) and also lead (Pb) and Cd exhibited spatial similarity. Manganese (Mn) and Cr exhibited point source characteristics such as the concentrations at a point much higher than the surrounding area. The potential ecological risk in the northern region belonged to the moderate risk level category. Cd contributed over 90% to the potential ecological risk. The health risk among children was higher than that among adults. The major exposure pathways were different for adults and children. Exposure, as shown using Hazard Index (HI), to adults was mainly through the skin contact route, while to children was through both the skin contact and ingestion route. The primary CR (carcinogenic risk) to adults was through the inhalation route, while that to children was through the ingestion route. In both children and adults, Cr was the main contributor to HI and CR. According to the Monte Carlo simulation results, the cumulative probability of exceeding the critical value of HI for children was approximately 2.8-3.0 times that for adults. According to the sensitivity analysis results, non-carcinogenic risk prevention should begin mainly by reducing exposure duration and skin contact. The cancer risk may be reduced primarily by decreasing the exposure duration and controlling ingestion. The PMF (Positive Matrix Factorization) source analysis revealed that Pb mainly came from transportation sources. In addition, Cu, Pb, and Mn were derived mainly from agricultural sources. Cr was derived mostly from a natural source, and Cd originated mainly from an industrial source.

Human Exposure Assessment of Tris (1-chloro-2-propyl) phosphate (TCIPP) via Dermal Contact with Car Dust

Tris (1-chloro-2-propyl) phosphate (TCIPP) synthesis halogenated organophosphate compound that is widely used as flame retardants and plasticizer. The toxicity of TCIPP has led to concern about human exposure. Dermal absorption via indoor dust (particularly cars) represents one of the major human exposure pathways. The present study reports on the investigation of the levels of TCIPP in car dust samples from Basrah Iraq. The samples were collected from 24 private cars in different years of manufacture and countries. After the extraction and purification, samples were analysed by GC-EI/MS. Concentrations of TCIPP in dust samples were between 784 and 29478 ng/g with mean and median concentrations of 5162, 2696 ng/g respectively. Based on the manufactured country, Korean cars were the lowest levels of TCIPP comparing with Chinses,Japanese and the USA manufacture cars. Estimations daily intake via dermal absorptions showed that taxi drivers are more exposed to those of the two age groups (adults and toddlers), with an average of 0.124, 0.493 and 0.842 (ng/kg bw/day) for adults, toddlers and taxi drivers respectively. Those results were several orders of magnitude lower than the corresponding reference dose (RfD values).

Toxicity evaluation of the contaminated area of Crotone from biological indicators: a multispecies approach

Contamination of terrestrial and aquatic ecosystems by toxic industrial waste has become a major issue in many countries. Of particular concern is the reuse of toxic hazardous waste in construction materials. This paper examined for the first time the chemical and radiation ecotoxicity of site-specific Technological Enhanced Naturally Occurring Radioactive Materials (TENORM) residues from phosphate processing industry in soil environmental matrices through bioindicators. The area under investigation was the former industrial district of Crotone (Calabria, Italy), recently included within the Sites of National Interest (SIN), comprising the 42 Italian national priority contaminated sites. Major biological exposure pathways considered were absorption and bioaccumulation. The marine bacterium Vibrio fischeri and the freshwater crustacean Daphnia magna were employed as aquatic bioindicators, while for the soil ecosystem, the seeds of Sorghum saccharatum and Lepidium sativum were used. Selection of test species aimed at assessing the toxicity of wastes in soil as well as in freshwater or marine systems. Results indicated V. fischeri as the most sensitive of all the species tested (5.56 g/L), while D. magna was found to be affected at 94.27 g/L. An overall inhibition was observed in seedling growth as compared to control at the highest concentration of the pollutants (100 g/L), while seed germination was not adversely affected by the pollutant. At this preliminary level, data indicated a potential risk for biodiversity of the area. In fact, the measured toxicity thresholds, even if above 100 mg/L, are comparable to concentrations of the toxicants spread all over the territory of Crotone.

Human exposure to short-chain chlorinated paraffins and organophosphate flame retardants in relation to paired multiple sources

In this study, the levels and distributions of short chain chlorinated paraffins (SCCPs) and organophosphate flame retardants (OPFRs) were determined in 10–88 aged human serum/hair and their paired multiple exposure sources, including one-day composite food, drinking water, and house dust. The average concentration of SCCPs and OPFRs were respectively 6313 and 176 ng/g lipid weight (lw) in serum, 1008 and 108 ng/g dry weight (dw) in hair, 1131 and 27.2 ng/g dw in food, not detected and 45.1 ng/L in drinking water, and 2405 and 864 ng/g in house dust. The levels of SCCPs in serum of adults were significantly higher than those of juvenile (Mann-Whitney U test, p < 0.05), whereas gender showed no statistically significant difference in SCCPs and OPFRs levels. In addition, there were significant relationships of OPFR concentrations between serum and drinking water as well as hair and food using the multiple linear regression analysis, whereas no correlation was observed for SCCPs. Based on the estimated daily intake, the major exposure pathway for SCCPs was food, while for OPFRs, it was food and drinking water with three order magnitude safety margin.

Mechanochemical destruction of per- and polyfluoroalkyl substances in aqueous film-forming foams and contaminated soil.

Per- and polyfluoroalkyl substances (PFASs) are a class of synthetic chemicals of concern that exhibit extreme persistence within the environment and possess physicochemical properties that are resistant to targeted degradation. Comprising substantial concentrations of PFASs, aqueous film-forming foams (AFFFs) present a major exposure pathway to the environment having been applied to land at firefighting-training sites globally for decades. This has led to significant contamination of environmental media. Herein, we demonstrate that mechanochemical destruction (MCD) is an effective method for the destruction of PFASs in an AFFF concentrate and an authentic sample of PFAS-contaminated soil derived from a decommissioned firefighting training facility. Both targeted analysis and non-targeted analysis were used in this study to evaluate the degradation of PFASs in complex substrates during MCD treatment. Destruction efficiencies of target PFAS subgroups ranged from 99.88% to 100%. The only additive employed for MCD treatment was quartz sand, which was used only for the liquid AFFF sample, with no additives required for the destruction of PFASs in the contaminated soil. This confirms the viability of MCD for both the remediation of PFAS-contaminated land and the destruction of stockpiled AFFFs.

Cement Dust Exposure Alters Secretory Functions, Biochemical Profile and Morphology of Gastrointestinal Tissues in Rats Exposed to Cement Dust.

Asides direct gastrointestinal exposure, inhalation route is another major xenobiotic exposure pathway to the gastrointestinal tract via mucociliary escalator. This triphasic study assesses cement dust inhalatory exposure effect on the possible alterations of the gastrointestinal tissues and secretion. 72 male, sixteen (16) weeks old Wistar rats were randomized into 3 different phases of 24 animals. Each phase comprised of 3 group of 8 animals. Group 1 (control) were sham-operated with clean ambient air, group 2 (14-days exposed) were exposed to cement dust for 14days, and group 3 (28-day exposed) were exposed to cement dust for 28 days. Biochemical indices including superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), sulfhydryl group, carbonyl group, Na+-K+ATPase pump activity, Nitric oxide (NO) were investigated spectrophotometrically in gastric and hepatic tissues while histopathology was studied using standard procedure. There was significant increase in the level of MDA, NO and carbonyl- an observation that contrasts with the level of CAT, SOD and sulfhydryl; no significant difference in Na+-K+-ATPase pump was observed in the exposed groups compared with control. Histopathological alterations in salivary gland and gastric tissues includes edema, inflammatory cell infiltration and vascular congestion. There was significant alteration in basal salivary, gastric and biliary secretions; increased stimulated salivary and gastric secretion via cholinergic stimulation. Conclusively, histopathological and spectrophotometric analyses reflect that inhalatory experimental exposure to cement dust significantly alter gastrointestinal secretions and predisposes the gastrointestinal tract to an array of deleterious effects via protein oxidation and antioxidant depletion and tissue peroxidation.

Dietary Intake Contributed the Most to Chlorinated Paraffin Body Burden in a Norwegian Cohort.

Determining the major human exposure pathways is a prerequisite for the development of effective management strategies for environmental pollutants such as chlorinated paraffins (CPs). As a first step, the internal and external exposure to CPs were quantified for a well-defined human cohort. CPs in participants' plasma and diet samples were analyzed in the present study, and previous results on paired air, dust, and hand wipe samples were used for the total exposure assessment. Both one compartment pharmacokinetic modeling and forensic fingerprinting indicate that dietary intake contributed the most to body burden of CPs in this cohort, contributing a median of 60-88% of the total daily intakes. The contribution from dust ingestion and dermal exposure was greater for the intake of long-chain CPs (LCCPs) than short-chain CPs (SCCPs), while the contribution from inhalation was greater for the intake of SCCPs than medium-chain CPs (MCCPs) and LCCPs. Significantly higher concentrations of SCCPs and MCCPs were observed in diets containing butter and eggs, respectively (p < 0.05). Additionally, other exposure sources were correlated to plasma levels of CPs, including residence construction parameters such as the construction year (p < 0.05). This human exposure to CPs is not a local case. From a global perspective, there are major knowledge gaps in biomonitoring and exposure data for CPs from regions other than China and European countries.

Soil exposure is the major fluoride exposure pathways for residents from the high-fluoride karst region in Southwest China

In the karst areas of southwest China, soil fluoride levels are higher than in China (478 mg kg−1) and world (200 mg kg−1). High levels of F in the environment might pose a health risk to humans. The comprehensive exposure risk must be studied in this area. Herein, samples of crops and soil were collected from Bijie City, a typical karst area in southwest China, to investigate the pollution level and evaluate the comprehensive F exposure risk. The single-factor index (PFw) and the geological accumulation index (Igeo) were used. The hazard index (HI) was applied to assess exposure risk from multiple exposure routes. The results revealed that there is considerable F contamination in soil and crops in the study area. Average soil total fluorine (Ft) was 1139.13 mg kg−1, and soil water soluble F (Fw) was 3.792 mg kg−1. In corn, rice, wheat, and potatoes, F contents were 1.167–9.585, 1.222–6.698, 1.587–9.976, and 1.797–9.143 mg kg−1, respectively. The mean values of HI were 4.45 and 2.42 for children and adults, respectively, > 1, showing potential health risk exists. Youngsters are at a greater exposure risk than adults. From the results of contribution ratios of different exposure routes for health risk, the major exposure risk was determined to be from soil exposure. Based on this, we suggest that risk managers mainly strive to control the soil fluoride level and implement the risk education and communication.

Spatially Resolved Distribution, Sources, Exposure Levels, and Health Risks of Heavy Metals in

In the present study, a total of 64 road dust samples were collected from five different functional areas (residential, commercial, parks, high-traffic, and industrial) in urban Lucknow to assess the accumulation, distribution, and health risk of heavy metals (HMs) (i.e., Fe, Mn, Zn, Cu, Pb, Cd, As, Cr and Ni). Acid digestion methods were used to analyze HMs, followed by inductively coupled plasma-mass spectrometry (ICPMS). The ascending frequency of HMs was Cd < As < Ni < Cr < Pb < Cu < Zn < Mn < Fe for all different functional areas. Almost all HMs exceed the limits of Indian natural soil background values (INSB) across all functional areas. The pollution assessment results reveal that the urban road dust of Lucknow is highly enriched with Zn and Pb, causing deterioration of dust quality. The spatial distribution of HMs shows that road dust found in the central and southwestern zones of the Lucknow urban area are more contaminated than in other areas. The ecological risk assessment demonstrates that Cd was the highest risk contributor, followed by Pb, Zn and Cu. The result of the health risk assessment i.e., the cumulative hazard index (HI) and the cumulative lifetime cancer risk (LCR), reveal that children (mean HIchildren = 1.26, LCRchildren = 0.000187) are more vulnerable to HM exposure than adults (HIadults = 0.14, LCRadults = 0.0000804). For carcinogenic and non-carcinogenic risk, ingestion appears to be the major pathway of HM exposure in both age groups. It is alarming that all studied four carcinogenic HMs were found in concentrations higher than 1 × 10−6 (the permissible limit for humans). This indicates slight chances of developing cancer for both age groups in all functional areas.

Urinary phthalate metabolites and phenolics in women of childbearing age and their association with thyroid hormones: a comparison study of fasting status

[BACKGROUND AND AIM] Exposure to parabens and phthalates has been associated with thyroid hormones in humans. Epidemiologic observations, however, are often inconsistent depending on population, probably due to different susceptibility or other factors such as exposure misclassification. Fasting status may influence the urinary levels of many chemicals, especially when their major exposure pathways are related to diet. In the present study, we assessed the associations of urinary phthalate metabolites and phenolics with thyroid hormones in non-pregnant women of child-bearing age in Korea (20-49 years of age), considering fasting status. [METHODS] As a fasting population, we recruited women (n=254) who visited four hospitals after &amp;#x3e;9 hr of fasting between 2015 and 2016. From the fasting women, we measured phthalate metabolites and parabens in urine, and thyroid hormones in serum. Non-pregnant women of the same age group, who were not asked to fast, was chosen from KoNEHS Cycle 3 (2015-2017) (phthalate metabolites (n=341) and phenolics (n=340)). [RESULTS] Urinary concentrations of MEHHP, MEOHP, MBzP, and BPA were &amp;#x3e;2 folds higher in the non-fasting women, and those of MeP were higher in the fasting women. Regardless of fasting status, MeP and EtP levels showed significant negative association with both total and free T4. DEHP metabolites also showed negative associations with free T4 but positive associations with total T3. However, associations of MBzP and BPA with thyroid hormones varied by the fasting status, which might be due to the influence of diet on their urinary concentrations. [CONCLUSION] While certain chemicals like EtP and to lesser extent DEHP are known to be delivered through dietary factors, consistent associations with altered thyroid hormones regardless of fasting status are noteworthy. [KEYWORDS] thyroid hormones; fasting; phthalates; phenolics [Acknowledgement] This work was supported by grants from National Research Foundation of Korea (NRF) (NRF-2020R1A2C3011269 and NRF-2022R1C1C2006982).

Source apportionment and risk assessment of heavy metals in urban soils from a central China city by using positive matrix factorization model coupled with Monte Carlo simulation

The concentrations of As, Cd, Co, Cu, Mn, Ni, Pb and Zn in 78 urban soil samples from Zhengzhou, Henan Province, China were determined in the study. The mean values of the eight heavy metals were lower than the natural background reference values of soils from Henan Province, with the exception of Cd and Pb. However, the peak values for six species of the elements exceed the corresponding reference values, indicating enrichment of these metals in urban soils in Zhengzhou City, especially for Cd and Pb. The spatial distribution patterns showed that levels of As, Co, Mn and Ni decreased gently from northwest to southeast without hot-pot area, whereas Cd, Cu, Pb and Zn were with significant spatial variability. PMF model coupled with Pearson’s correlation analysis was performed to apportion and quantify possible sources of the eight elements. Four Factors (natural source, industrial production, agricultural activities and traffic discharges) were distinguished and their respective contribution rates were 18.73%, 33.22%, 23.91% and 24.14%, respectively. Results of uncertainty analysis confirmed that the all four source Factors based on the PMF model were reliable. Furthermore, the probability distribution of health risk assessed by means of Monte Carlo simulation revealed that non-carcinogenic risks associated with heavy metals were acceptable for both adults and children, while the total carcinogenic risk values remained relatively high. Additionally, the children were more susceptible to health risks in comparison to adults, and the ingestion way was considered to be the major exposure pathway. The results of source-oriented health risk demonstrated that the agricultural source was the major contributor to health risks, which was characterized by As, Ni and Co.

Distribution, source, and health risk assessment of polycyclic aromatic hydrocarbons in the soils from a typical petroleum refinery area in south China.

The ubiquity of polycyclic aromatic hydrocarbons (PAHs) in soils in petroleum refining areas is an important problem affecting human and ecological safety. In this study, 103 topsoil (0-0.50m) samples were collected from a retired petroleum refinery area in Guangdong province, south China. The PAHs concentrations were determined by ultrasonic extraction and gas chromatography-mass spectrometry detection methods. Twelve PAHs controlled priority listed by the US Environmental Protection Agency (USEPA) were investigated. The results revealed that the concentration of Ʃ12PAHs ranged from 2100 to 5200µgkg-1, with a mean value of 3741.66µgkg-1. The site was dominated by high rings PAHs (4-, 5-, and 6-ring), contributing 81.96% to Ʃ12PAHs. The concentrations of 9 kinds of PAHs exceeded the Dutch soil quality standard. Besides, the PAHs were primarily distributed in the storage tank area and with high levels of contamination. The results of hierarchical cluster analysis (HCA) and principal component analysis (PCA) indicated that coal combustion was the source of PAHs in topsoil, followed by petroleum dripping and traffic emissions. The incremental lifetime cancer risk (ILCR) modeling illustrated that soil ingestion was the major pathway of PAH exposure for both adults and children. Notably, the total noncarcinogenic human health risk due to PAHs was within the limit of 1, while the carcinogenic risks alone caused by benzo(a)pyrene via soil ingestion to adults and children were obviously beyond the USEPA limit (1.00E -06). Therefore, PAHs in the petroleum refinery areas have potential carcinogenic hazards to human health, the area should be remediated before reuse.

Phthalates in dormitory dust and human urine: A study of exposure characteristics and risk assessments of university students

Phthalate diesters (PAEs) are prevalent and potentially toxic to human health. The university dormitory represents a typical and relatively uniform indoor environment. This study evaluated the concentrations of phthalate monoesters (mPAEs) in urine samples from 101 residents of university status, and the concentrations of PAEs in dust collected from 36 corresponding dormitories. Di-(2-ethylhexyl) phthalate (DEHP, median: 68.0 μg/g) was the major PAE in dust, and mono-ethyl phthalate (47.9 %) was the most abundant mPAE in urine. The levels of both PAEs in dormitory dust and mPAEs in urine were higher in females than in males, indicating higher PAE exposure in females. Differences in lifestyles (dormitory time and plastic product use frequency) may also affect human exposure to PAEs. Moreover, there were significant positive correlations between the estimated daily intakes of PAEs calculated by using concentrations of PAEs in dust (EDID) and mPAEs in urine (EDIU), suggesting that PAEs in dust could be a significant source of human exposure to PAEs. The value of EDID/EDIU for low molecular weight PAEs (3–6 carbon atoms in their backbone) was lower than that of high molecular weight PAEs. The contribution rate of various pathways to PAE exposure illustrated that non-dietary ingestion (87.8 %) was the major pathway of human exposure to PAEs in dust. Approximately 4.95 % of university students' hazard quotients of DEHP were >1, indicating that there may be some health risks associated with DEHP exposure among PAEs. Furthermore, it is recommended that some measures be taken to reduce the production and application of DEHP.

Per- and polyfluoroalkyl substances in drinking water and hypertensive disorders of pregnancy in the United States during 2013-2015.

Background:Per- and polyfluoroalkyl substances (PFAS) widely exist in the environment and human bodies. Contaminated drinking water is one of the major exposure pathways for humans. Previous studies found weak or moderate associations between PFAS and hypertensive disorders of pregnancy (HDP).Methods:We obtained the number of births and counts of HDP cases for singleton births multiply stratified by county, maternal age, race, education, smoking status, and parity from CDC WONDER, and PFAS water concentrations from EPA UCMR3 data in the United States during 2013–2015. We used binomial regression on the multiply stratified HDP data to produce equal effect estimates and standard errors to those that would be derived from using individual-level data on binary HDP status and demographic covariates in logistic regression.Results:After adjusting for demographic covariates, we found small but statistically significant positive associations between HDP and population-weighted average water concentrations (ng/L) of all four PFAS: Odds ratio (OR) = 1.009, 95% CI = (1.001, 1.016) per IQR increase in perfluorooctanoic acid (PFOA); 1.030, 95% CI = (1.021, 1.040) per IQR increase in perfluorooctane sulfonate (PFOS); 1.008, 95% CI = (1.005, 1.011) per IQR increase in perfluoroheptanoic acid (PFHpA); 1.007, 95% CI = (1.004, 1.010) per IQR increase in perfluorohexane sulfonic acid (PFHxS), and 1.032, 95% CI = (1.022, 1.042) per IQR increase in the sum of four PFAS. Further adjustment for coexposures reversed the effect of PFOA from positive to inverse, and attenuated the effects of PFOS and PFHxS toward the null. After drinking water to serum concentration conversions, our effect estimates for PFOA, PFOS, and PFHxS are similar to previous studies.Conclusions:We found a weak positive association between the PFAS mixture and HDP, although the generalizability is subject to inherent limitations of the public-available datasets.

Climate Change Vulnerability Assessment: An Evaluation of Social Dimension

Climate change vulnerability is the function of exposure, sensitivity, and adaptive capacity of its natural and socioeconomic systems. Following spatial “scale” of the assessment, administrative-territorial units were selected for this study. A field survey questionnaire was used to collect data for the study based on the sample size of 500 questionnaires that was administered to household heads in the study area. In the questionnaire, questions were designed to give respondents the opportunity to choose from several alternatives given in the instrument while descriptive statistics was for the analysis of data. Descriptive statistics analysis based on mean ranking was carried out to identify the level of peoples’ vulnerability to climate change in the study area. The exposure assessment was based on the response analysis of baseline information. The sensitivity assessment for the study was analyzed by using physiographical and socioeconomic characteristics, described by a set of specific indicators and responses of the residents. The adaptive capacity was captured by general economic and agricultural indicators, taking into consideration the major occupation the predominant lifestyle of the residents. Through a ranking approach, the relative vulnerability of each ATU was calculated by summing its sensitivity and adaptive capacity ranks; the latter were obtained as combinations of their primary indicator ranks, arranged in an increasing and decreasing order, respectively. The major climate change exposure pathway in the study area were reduction in green environment, decrease in total annual rainfall, warmer weather, early cessation of rainfall, late on-set of rainfall and shrinkage of water bodies. The major sensitivity to climate change was decrease in crop yield, whereas increase in cost of food crops, drought incidents, famine, poverty, indiscriminate falling down of trees and disaster. It was also established that the major adaptive strategies to climate change in the study area were irrigation farming, use of organic manure, planting of drought tolerant varieties and early planting.

Quantifying exposure source allocation factors of pesticides in support of regulatory human health risk assessment

One of the challenges while assessing the aggregate exposure risk of pesticides is quantifying exposure doses from various exposure pathways. To address this issue, a regulatory screening approach is proposed for evaluating pesticide allocation factors (AFs) for major exposure pathways for rural and urban residents. This was achieved by integrating dynamiCrop and other screening models to estimate the potential human intake of residues from major crops at harvest, livestock products, and main environmental media (air, water, and soil). The AFs were calculated from the average daily dose factors (ADDFs) of pesticides via major exposure pathways, where a large AF of an exposure pathway indicates that a greater margin of exposure should be given to that exposure pathway. The simulated results for many current-use pesticides showed that the ingestion of crops had pesticide AFs close to 1.0, which indicated that the crop exposure pathway contributed to a significant portion of the total exposure to pesticides. In contrast, for legacy pesticides with high lipophilicity and low degradability in the environment, the simulated AFs for major environmental compartments (air, freshwater, and soil) accounted for relatively large exposures. As legacy pesticides have been banned globally, exposure pathways via the food web and environmental media cannot be neglected because of their high lipophilicity and environmental persistence. Although other factors such as geographical conditions and living habits should be considered to improve the spatial resolution of the model, the method proposed in this study can serve as a preliminary tool to conduct screening-level risk assessments for populations by considering the allocated exposure to pesticides via major exposure pathways.