Dermal Exposure Routes Research Articles

Comparative influences of dermal and inhalational routes of exposure on hazards of cleaning product ingredients among mammalian model organisms.

Health risks resulting from dermal or inhalational exposures are frequently assessed based on rodent oral toxicity information due to a lack of species- or route-specific toxicity data. Default uncertainty factors (UFs; e.g., 10-fold) are also applied during risk assessments to account for variability such as inter-species, intra-species, exposure duration, dose-response, and route-to-route extrapolations. However, whether rodent oral data and a default UF approach can provide adequate protection for other mammalian species under dermal or inhalational exposure scenarios remains understudied, particularly for cleaning product ingredients. Therefore, we collated and examined publicly available median lethal dose (LD50), no-observed-adverse-effect level (NOAEL) and lowest-observed-adverse-effect level (LOAEL) values from different types of standard mammalian toxicity studies for rats (dermal and inhalational), mice, rabbits, guinea pigs, and dogs (oral, dermal and inhalational) using the Cleaning Product Ingredient Safety Initiative (CPISI) database. Probabilistic hazard assessments using chemical toxicity distributions (CTDs) were subsequently conducted, and threshold concentrations (TCs) and 95% confidence intervals (95% CIs) were derived to identify thresholds of toxicological concern (TTCs). Relative sensitivities among or between mammalian species, exposure routes, and chemical classes were also compared based on calculated TC5s and 95% CIs to support future toxicology studies and hazard and risk assessments. We then identified uncertainty factors (UFs) using both CTD comparisons and individual UF probability distributional approaches. Based on available rodent inhalational data, chemical category-specific UFs were derived for ethers. Additionally, we also determined whether default UFs of 10 or 100 would be protective for various distributions of cleaning product ingredients. Our novel observations among these routes of exposure and common mammalian model organisms appear particularly useful for read across and screening-level health hazard and risk assessments when limited data exists for specific chemicals.

Unravelling the role of surface modification in the dermocompatibility of silver nanoparticles in vitro and in vivo

A clearer picture of interactions between differently coated silver nanoparticles (AgNPs) and biological interfaces that are confronted with by the dermal exposure route is of utmost importance for the risk assessment of various AgNPs-based formulations utilized in the medical and dermocosmetic fields. This work sought to understand how surface modification of AgNPs, especially those produced by green synthesis strategy, affects the surface chemistry and dermocompatibility. Phytosynthetized AgNPs diverse in bio-reducing/capping agents i.e. chlorogenic acid, glycyrrhizic acid and gallic acid, were prepared by a bioinspired green approach and characterized in terms of size, shape, crystal phase, surface charge, structure and antioxidant activity. Chemically synthetized AgNPs stabilized by trisodium citrate or polyvinylpyrrolidone were also analyzed for comparison. The biological test results illustrate that varying coating material for AgNP stabilization results in differential toxicity against dermal microbes and HaCaT keratinocytes in vitro and affects dermal absorption through intact/compromised skin in vivo. Among all test samples, the citrate-stabilized AgNPs displayed the maximum cytotoxicity and dermal absorption. It is also of interest to note that the phytosynthetized AgNPs with chlorogenic acid exhibited superior antioxidant activity, attenuated cytotoxicity and minimal skin deposition, while those modified with glycyrrhizic acid demonstrated a preferentially antibacterial activity against the pathogenic (Escherichia coli and Staphylococcus aureus) over the beneficial strains (Staphylococcus epidermidis) inhabiting human skin. Furthermore, percutaneous absorption of AgNPs into live epidermis was observed on all 7–13 nm sized AgNPs, irrespective of surface coating, with more pronounced skin deposition of silver species occurring for the chemically-synthetized AgNPs within compromised skin. Given all these results, it is concluded that surface modification with particular phytochemicals may render AgNPs with enhanced dermocompatibility or antimicrobial activity. This study provides a basis for risk assessments of phytosynthetized AgNPs in consumer products and suggests the possibility of tailoring AgNPs applicability via green chemistry approach.

Groundwater contamination and health risk assessment across an urban gradient: Case study of Onitcha metropolis, south-eastern Nigeria

Urban population growth in south-Eastern Nigeria and associated proliferation of built-up areas predispose groundwater to contaminants of anthropogenic origin. This study compared the groundwater quality across an urban gradient, in Onitsha, a notable urbanized region and beehive of commercial activity in southeastern Nigeria. Groundwater samples (n = 120) from sixty boreholes tapping into aquifers spanning major settlement clusters at upper Iweka, Mgbuka and Nkpor, were sampled over 5-months from August to December 2019. Faecal coliforms, water-soluble metals, and nutrients (nitrates and phosphates) were estimated in groundwater samples. Noncarcinogenic risks of heavy metals in ground water samples was estimated for Average daily dose (ADD) and Total Hazard Quotient (THQ) using both deterministic and probabilistic approaches. Concentrations of mercury and heavy metals (Fe, Pb, and Cd) estimated in water samples revealed a general exceedance of World Health Organization (2009) standards for drinking water. However, significantly higher Hg, Pb and faecal coliform levels (0.122 ± 0.03 mg/L, 0.115 ± 0.014 mg/L, 2.3 × 106 ± 300 MPN respectively) in groundwater of the more built-up areas of upper Iweka highlight increased chances of metals and pathogens impacts on water quality with increased urbanization. High incidence of nutrients (nitrates: 258.40 ± 62.1 and phosphorus: 33.05 ± 4.06 mg/L) in groundwater of less urbanized areas suggests impacts of fertilizer applications from greater agricultural activity. Probabilistic estimates for heavy metals in ground water from Onitsha via ingestion route, showed that Upper Iweka had the highest HQ (3.262) followed by Mgbuka (2.1233) and Nkpor (2.0187). On the other hand, estimates showed that Mgbuka had the highest HQ (0.0241) followed by Nkpor (0.016) and Upper Iweka (0.014) for dermal exposure routes. Strategic mitigation measures including urban planning and infrastructural upgrade are recommended to protect the water resources, prevent further groundwater contamination and reduce population health risks emanating from poor drinking water sources.

Levels and risk assessments of polycyclic aromatic hydrocarbons in soil situated around unlined dumpsite in Okpunoeze, Nnewi, Nigeria

ABSTRACT Polycyclic aromatic hydrocarbons (PAHs) are organic pollutant found in the soil which can cause several health effects to human beings and the environment. The study was aimed at evaluating the concentration level of PAHs of soil located around an open/unlined dumpsite. 32 samples comprising of 16 samples each of upstream and downstream (control) were obtained in both seasons. The concentration of PAHs was ascertained using gas chromatography interfaced with a flame ionisation detector (FID). Toxic and mutagenic risk assessments were employed to evaluate the toxicity risk. The probability of cancer health risks was determined through dermal and ingestion routes. Molecular PAHs ratios were used to predict the potential sources. The PAHs concentrations in the upstream and downstream ranged from ND – 120.6 µg/kg and 0.03–7.08 µg/kg respectively. Total PAHs concentrations in the upstream and downstream ranged from 20.57–144.28 µg/kg and 11.43–18.84 µg/kg respectively. The upstream samples PAH concentrations were greater than the downstream site in both seasons. The PAH concentration in the wet season was greater than the dry season values, which was possibly due to leachate pollution. The four-ringed PAHs were the most prominent in the PAHs, while the six-ringed PAHs were the least dominant PAHs for both seasons. Benzo(a)pyrene values estimated from Ba and Ba were found to have possible chances of carcinogenic and mutagenic risks in the soil samples for both upstream and downstream locations. There were no chances of possible carcinogenic risks through ingestion and dermal exposure routes. The values of diagnostic ratios obtained confirmed that PAHs sources are predominantly from pyrolytic sources for upstream location. Downstream diagnostic ratios values had a slightly dominant petrogenic source than the pyrolytic sources.

Assessing secondhand and thirdhand tobacco smoke exposure in Canadian infants using questionnaires, biomarkers, and machine learning

BackgroundAs smoking prevalence has decreased in Canada, particularly during pregnancy and around children, and technological improvements have lowered detection limits, the use of traditional tobacco smoke biomarkers in infant populations requires re-evaluation.ObjectiveWe evaluated concentrations of urinary nicotine biomarkers, cotinine and trans-3’-hydroxycotinine (3HC), and questionnaire responses. We used machine learning and prediction modeling to understand sources of tobacco smoke exposure for infants from the CHILD Cohort Study.MethodsMultivariable linear regression models, chosen through a combination of conceptual and data-driven strategies including random forest regression, assessed the ability of questionnaires to predict variation in urinary cotinine and 3HC concentrations of 2017 3-month-old infants.ResultsAlthough only 2% of mothers reported smoking prior to and throughout their pregnancy, cotinine and 3HC were detected in 76 and 89% of the infants’ urine (n = 2017). Questionnaire-based models explained 31 and 41% of the variance in cotinine and 3HC levels, respectively. Observed concentrations suggest 0.25 and 0.50 ng/mL as cut-points in cotinine and 3HC to characterize SHS exposure. This cut-point suggests that 23.5% of infants had moderate or regular smoke exposure.SignificanceThough most people make efforts to reduce exposure to their infants, parents do not appear to consider the pervasiveness and persistence of secondhand and thirdhand smoke. More than half of the variation in urinary cotinine and 3HC in infants could not be predicted with modeling. The pervasiveness of thirdhand smoke, the potential for dermal and oral routes of nicotine exposure, along with changes in public perceptions of smoking exposure and risk warrant further exploration.

Polycyclic Aromatic Hydrocarbon (PAH) Pollution and its Associated Human Health Risks in the Niger Delta Region of Nigeria: a Systematic Review

The frequent incidents of oil spills and other forms of pollution arising from crude oil exploration and exploitation (OEE) in the Niger Delta have caused several investigations on Polycyclic Aromatic Hydrocarbons (PAHs) pollution. This study aimed at developing a comprehensive report on PAH pollution and its human health risks recorded in the Niger Delta. Studies were extracted from Google Scholar, PubMed, and ResearchGate using a defined selection criterion. The quality of each study was assessed using the Newcastle – Ottawa Scale. Thirty-eight studies were selected with the majority reporting on PAH pollution in aquatic environments. Across all the selected studies, the total number of PAHs recorded ranged from 7 to 28 PAH congeners. Also, PAH potential sources reported in the studies were of pyrogenic and petrogenic sources. PAH concentrations recorded in water, sediment, aquatic organisms (fish and shrimp), soil, dust, and crop samples ranged from below detection limit (BDL) to 450 ± 117.9 mg/L, BDL to 1821.5 mg/kg, 0.005 to 1.098 mg/kg, ND to 4154 ± 3461 mg/kg, 165.1 to 1012 mg/kg, and 0.020 to 3.37 mg/kg, respectively. The majority of the selected studies reported PAH levels which were higher than the permissible limits. Incremental Lifetime Cancer Risk (ILCR) assessment of PAHs in samples ranged from low to high via ingestion and dermal routes of exposure to humans. It is recommended that the Federal Government of Nigeria promotes environmentally friendly operations of OEE. Future studies should focus on PAH pollution in farmlands, ambient air, and the associated human and ecological health risks.

Chemical exposures from upholstered furniture with various flame retardant technologies

Upholstered furniture is often manufactured with polyurethane foam (PUF) containing flame retardants (FRs) to prevent the risk of a fire and/or to meet flammability regulations, however, exposure to certain FRs and other chemicals have been linked to adverse health effects. This study developed a new methodology for evaluating volatile organic compound (VOC) and FR exposures to users of upholstered furniture by simulating use of a chair in a controlled exposure chamber and assessing the health significance of measured chemical exposure. Chairs with different fire‐resistant technologies were evaluated for VOC and FR exposures via inhalation, ingestion, and dermal contact exposure routes. Data show that VOC exposure levels are lower than threshold levels defined by the US and global indoor air criteria. Brominated FRs were not detected from the studied chairs. The organophosphate FRs added to PUF were released into the surrounding air (0.4 ng/m3) and as dust (16 ng/m2). Exposure modeling showed that adults are exposed to FRs released from upholstered furniture mostly by dermal contact and children are exposed via dermal and ingestion exposure. Children are most susceptible to FR exposure/dose (2 times higher average daily dose than adults) due to their frequent hand to mouth contact.

Human health risk assessment of arsenic in a region influenced by a large coal-fired power plant

Previous studies in the largest coal mining region of Brazil showed the strong influence of the coal-fired power plant in spatial distribution of As, especially in prevailing wind direction. However, it was not evaluated the risk of As on the local population. Thus, this study aims to assess the human health risk of As in a region under influence of atmospheric deposition of As from the coal-fired power plant. The human health risk assessment model was based on established by the U.S. Environmental Protection Agency (USEPA). It estimate the average daily dose (ADD), non-carcinogenic (HQ) and carcinogenic risk by in oral, dermal and inhalation exposure routes, as well as, the contribution of each via to ADD, HQ and carcinogenic risk to soil and air. Separately, both air and soil exposure pathways show HQ and HI below the risk threshold (< 1). However, when considerate the sum of both exposure pathways in the worst scenario of As contamination in air (maximum concentrations) there are a carcinogenic risk in the most of evaluated areas, including in a control area. The maximum values of As in PM10 contribute to health risk by air inhalation pathway (1.45 µg/m3). Inhalation pathway presents the major contribution to ADDair and ADDtotal. However, oral and dermal routes were more important to ADDsoil. The study reveals that there is a carcinogenic risk for exposure to As at a distance of almost 10 km from the coal-fired power plant.

Estimating Health Risks to Children Associated with Recreational Play on Oil Spill-Contaminated Beaches.

The human health impact from exposure to contaminated shorelines following an oil spill event has been investigated to some extent. However, the health risks to children have largely been characterized through the use of surveys and extrapolation from adult health outcomes. There is limited information on children’s behaviors during beach play requiring assumptions made based on observations from play activities in home settings. The Beach Exposure and Child Health Study (BEACHES) quantified specific beach activities that can be used to inform human health risk assessments of children playing on beaches impacted by oil spills. The results of this study characterize children’s risk of cancer from exposure to oil spill chemicals by incorporating exposure-related information collected from the BEACHES study and by assuming oral, dermal, and inhalation exposure routes. Point risk estimates are compared with a previous, similar study that applied default exposure parameter values obtained from the published literature. The point risk estimates informed by BEACHES data are one order of magnitude lower compared with the previous risk assessment, with dermal exposures the overall risk driver in both. Additional Monte Carlo simulations evaluating the BEACHES data provide ranges of health risks with the highest estimates associated with dermal and oral exposure routes.

Groundwater chemistry, distribution and potential health risk appraisal of nitrate enriched groundwater: A case study from the semi-urban region of South India

In recent years, an elevated concentration of nitrate in groundwater has been a growing problem on a global scale. It directly shows the adverse effects on human health via various intake pathways. Herein, the aim of the present study was to evaluate the nitrate concentration in groundwater and its associated human health risk in various age groups (females, males and children) in the investigated region. For this purposes, thirty groundwater samples were collected and analyzed physico-chemical parameters including nitrate concentration. The results showed that, the concentration of nitrate ranges from 14 to 82 mg/L and about 43.3% of these groundwater samples beyond the safe level of 45 mg/L according to Indian guidelines. The higher nitrate contamination is observed in the vicinity of Sarvepalli and Timmapur villages where groundwater chemistry is majorly influenced by anthropogenic sources. Health risks were assessed through oral/ingestion and dermal contact exposure routes for females, males and children population in the study region. Oral exposure was much higher than dermal contacts. For the non-carcinogenic risk, the HITotal values of groundwater in the investigated region varied from 0.313 to 1.976 (mean of 0.941) for males, 0.370 to 2.336 (mean of 1.112) for females and 0.443 to 2.694 (mean of 1.314) for children. The health risk assessment for nitrate divulged that 60%, 57% and 50% of groundwater samples pose a non-carcinogenic health risk for children, females and males, respectively.

Current practices underestimate environmental exposures to methamphetamine: inhalation exposures are important

Current practice for determining the exposure to methamphetamine in contaminated homes relies on the analysis of surface wipe sample to address direct contact exposures. The movement of methamphetamine into the air phase, and the potential for inhalation exposures to occur within residential homes contaminated from former clandestine manufacture or smoking of methamphetamine has been generally poorly characterised and understood. All available risk-based guidelines for determining safe levels of methamphetamine in residential properties do not include any consideration of the inhalation pathway as an exposure route. This study showed that methamphetamine can readily move from contaminated materials in a home into the air phase. This movement of methamphetamine into the air phase provides both an exposure pathway and a mechanism for the transfer of methamphetamine throughout a property. The inhalation exposure pathway has the potential to result in significant intake of methamphetamine, adding to dermal absorption and ingestion exposure routes. Guidelines that are established for the assessment of methamphetamine contaminated properties that ignore inhalation exposures can significantly underestimate exposure and result in guidelines that are not adequately protective of health. This study also demonstrates that sampling methamphetamine in air can be undertaken using commercially available sorption tubes and analytical methods.

Side-chain fluorotelomer-based polymers in children car seats.

Fabric and foam samples from popular children car seats marketed in the United States during 2018 were tested for fluorine content by particle-included gamma ray emission spectroscopy (PIGE, n=93) and X-ray photoelectron spectroscopy (XPS, n=36), as well as for per- and polyfluoroalkyl substances (PFAS) by liquid and gas chromatography mass spectrometry (LC/MS and GC/MS, n=36). PFAS were detected in 97% of the car seat samples analyzed with MS, with total concentrations of 43 PFAS (∑PFAS) up to 268ng/g. Fabric samples generally had greater ∑PFAS levels than foam and laminated composites of foam and fabric. The three fabric samples with the highest total fluorine content as represented by the highest PIGE signal were also subjected to ultraviolet (UV) irradiation and the total oxidizable precursor (TOP) assay. Results from these treatments, as well as the much higher organofluorine levels measured by PIGE compared to LC/MS and GC/MS, suggested the presence of side-chain fluorotelomer-based polymers (FTPs), which have the potential to readily degrade into perfluoroalkyl acids (PFAAs) under UV light. Furthermore, fluorotelomer (meth)acrylates were found to be indicators for the presence of (meth)acrylate-linked FTPs in consumer products, and thus confirmed that at least half of the tested car seats had FTP-treated fabrics. Finally, extraction of selected samples with synthetic sweat showed that ionic PFAS, particularly those with fluorinated carbons ≤8, can migrate from fabric to sweat, suggesting a potential dermal route of exposure.

Safety and health risk assessment methodology of dermal and inhalation exposure to formulated products ingredients

Consumers are commonly exposed to numerous chemical ingredients found in various formulated products especially household and personal care products. Therefore, identification of hazardous ingredients contained in those products should be performed at the early stages of product design to reduce the high cost of redesigning the products at the final stage. Thus, a systematic safety and health risk assessment methodology is required for the product formulation design. In this work, a two-step index-based methodology is presented to estimate the severity of the hazards and the magnitude of risks. In Tier 1 assessment, potential hazards of the ingredients were identified by following the Product Ingredient Safety Index (PISI). The basic toxicology information of ingredients was required for this assessment. In Tier 2 assessment, the extent of risks of the ingredients via dermal and inhalation exposure routes were evaluated. At this stage, the concentration of ingredients and the amount of exposure were considered. The value of Margin of Exposure (MOE) was used as an indicator in the development of Product Ingredient Exposure Index (PIEI). To demonstrate the proposed methodology, a case study on the evaluation of potential hazards and the risks from ingredients used in personal care product formulations were performed.

Entropy-Based Analysis of the Impact of Environmentally Sensitive Elements on Groundwater Quality of the Ameka Region of Southeast Nigeria: Medical Geology Implications

Understanding the impact of natural and modified environment on human health is a subject within the scope of medical geology. Ameka and its environs in southeastern Nigeria is known for intensive mining and agricultural activities that frequently predispose water resources to pollution by environmentally sensitive elements (ESEs). The present study analyzed the groundwater quality and associated probabilistic human health risks due to ESEs in Ameka area, using multiple indices and a novel health risk assessment framework, HHRISK. Entropy-weighted water quality index and other geochemical evaluation indices (including pollution index, enrichment factor, index of geoaccumulation, pollution index of groundwater, and quantification of contamination) revealed that all the groundwater samples from hand-dug wells and boreholes were extremely polluted and hence unsuitable for drinking. The HHRISK model was utilized for ingestion and dermal exposure routes assessments. Results showed that all the samples pose very high carcinogenic and non-carcinogenic health risks. With respect to aggregated non-carcinogenic HHRISK, the order of health threat impact of the ESEs for children and adult populations is predicted as Cd > As > Se > Co > Ni > Pb > Mn > Zn > Cu > Fe. However, aggregated cancer risk for both populations followed the trend Ni > Cd > As > Pb. Furthermore, cumulative non-carcinogenic risk (HRQcum) and carcinogenic risk (CRcum) scores (for children and adults) exceeded standard limits in all the samples. However, the scores obtained for the adults were generally lower, implying that the children population is more vulnerable to both non-carcinogenic and carcinogenic health risks. Thus, there is urgent need to adopt environmentally-friendly pollution mitigation measures in the Ameka area.

Human health risk assessment for exposure to BTEXN in an urban aquifer using deterministic and probabilistic methods: A case study of Chennai city, India

The aquifer in Tondiarpet, Chennai, had been severely contaminated with petroleum fuels due to an underground pipeline leakage. Groundwater samples were analyzed quarterly for priority pollutants such as benzene, toluene, ethylbenzene, xylenes, and naphthalene (BTEXN) using purge and trap gas chromatography and mass spectrometer from 2016 to 2018. The maximum concentrations of BTEXN in groundwater at the site were found to be greater than the permissible limits significantly. Among the five sampling locations (MW1, MW2, MW3, MW4, and MW5), mean BTEXN levels were found to be higher near MW2, confirming the source location of petroleum leakage. Human health risk assessment was carried out using deterministic and probabilistic methods for exposure to BTEXN by oral and dermal exposure pathways. Risk analysis indicated that mean cancer and non-cancer risks were many times higher than the allowable limits of 1E-06 and 1 respectively in all age groups (children, teens, and adults), implying the adverse health effects. Oral exposure is predominately contributing (60–80%) to the total health risk in comparison to the dermal exposure route. Variability and uncertainty were addressed using the Monte Carlo simulations and the resultant minimum, maximum, 5th, 95th, and mean percentile risks were predicted. Under the random exposure conditions to BTEXN, it was estimated that the risk would become unacceptable for >98.7% of the exposed population. Based on the sensitivity analysis, exposure duration, and ingestion rate are the crucial variables contributing significantly to the health risk. As part of the risk management, preliminary remediation goals for the study site were estimated, which require >99% removal of the BTEXN contamination for risk-free exposures. It is suggested that the residents of Tondiarpet shouldn’t utilize the contaminated groundwater mainly for oral ingestion to lower the cancer incidence related to exposure to BTEXN.

Organic pollutants in indoor dust from Ecuadorian Amazonia areas affected by oil extractivism

Fifty-five household dust samples collected within six settlements surrounding oil production complexes along the Ecuadorian Amazonia were analysed to evaluate the occurrence and distribution of polycyclic aromatic hydrocarbons (PAHs), phthalates, alkylphenols (APs), bisphenol A (BPA), nicotine, organophosphorus flame retardants (OPFRs), polychlorinated biphenyls (PCBs), legacy organochlorine pesticides (OCs) and organophosphorus pesticides. Studied areas are mainly affected by gas flares emissions and oil spilling coming from extractivist operations and pesticides used in agriculture. Median ΣPAHs values ranged from 739 to 1182 ng g−1 and up to 52% of the PAH dust concentrations were associated to petrogenic activities from crude oil extraction, according to diagnostic ratios. ΣPAHs and toxic equivalents based on benzo[a]pyrene concentration (ΣTEQBaP, ng g−1) suggested similar toxicities among the different areas. Individual lifetime cancer risk (ILCRdust) was calculated for ingestion and dermal contact exposure routes and a non-acceptable total carcinogenic risk of up to 10−4 (one case per ten thousand people) was found for newborns from 0 to 3 years-old in Pimampiro area. Plasticisers and OPFRs were present in dust at maximum median concentrations of 332,507 ng g−1 (DEHP), 5,249 ng g−1 (DBP), 1,885 ng g−1 (BPA), 871 ng g−1 (TBOEP) and 122 ng g−1 (TEHP). Some dust samples from Ecuadorian houses had high maximum levels of legacy and modern pesticides such as chlorpyrifos (up to 44,176 ng g−1), 4,4′-DDT (12,958 ng g−1), malathion (34,748 ng g−1) and α+β-endosulfan (10,660 ng g−1) attributed to inappropriate use and storage of the pesticides. Finally, nicotine was seldom detected (36 ng g−1). The sources and risks of these compounds are discussed based on the activities carried out in the study areas and attending to an additional non-cancer risk assessment which showed high hazard quotients (HQ) and hazard indexes (HI) for DEHP, DBP, 4,4′-DDT, malathion, chlorpyrifos, naphthalene and benzo[a]pyrene in newborns and children up to 16 years-old.

Balancing chemical function with reduced environmental health hazards: A joint probability approach to examine antimicrobial product efficacy and mammalian toxicity

The fourth principle of Green Chemistry, a critically important area of sustainability science, identifies that substances should maintain intended functions while possessing limited intrinsic hazards to public health and the environment. In the present study, we empirically determined efficacy of 20 cleaning products against E. coli attachment to surfaces. Subsequently, probabilistic assessments using novel chemical efficacy distributions (CEDs) were conducted. Results for most chemicals indicated bacterial detachment with increasing concentration. Using a threshold concentration of 5th centiles, these cleaning product ingredients were predicted to detach E. coli (Lowest Observable Effect Concentration) at or below 0.7 (0.2, 2.2) mg L−1 for 5% of ingredients. We then employed chemical toxicity distributions (CTDs) to examine acute toxicity, based on currently available information, for common mammalian models. Results demonstrate that probabilities of associated hazards for rat (oral exposure route), mouse (oral exposure route), rabbit (dermal exposure route), and rat (inhalation exposure route) were 43.2%, 36.7%, 38.6% and 75.5%, respectively. A novel joint probability distribution analysis approach was then developed and applied to identify substances with various efficacy (CED) and hazard (CTD) characteristics. Our observations indicate that combining efficacy and toxicity information using joint probability curves may be useful for identifying classes of antimicrobial products, and other chemical classes, to optimize efficacy while minimizing environment and health hazards.

Risk assessment implications of site-specific oral relative bioavailability factors and dermal absorption fractions for polycyclic aromatic hydrocarbons in surface soils impacted by clay skeet target fragments

Risk assessment conclusions for a site may differ when using site-specific versus default values for the relative bioavailability factor (RBAF) and dermal absorption fraction (ABS.d), because these inputs affect both surface soil screening levels and risk/hazard estimates. Indeed, our case study demonstrates that different conclusions may be reached as to regulatory need for remedial action to protect human health when evaluating soil sampling data for seven carcinogenic polycyclic aromatic hydrocarbons (PAHs) using site-specific versus default TCEQ and USEPA residential soil screening levels. Use of site-specific RBAF and ABS.d values increased carcinogenicity-based TCEQ and USEPA surface soil screening levels for PAHs by 4.4- and 6-fold on average, respectively. Soil screening levels for PAHs were more sensitive to changes in ingestion exposure route parameters than to changes in dermal exposure route parameters. Accordingly, site-specific RBAF and ABS.d information has important implications for screening chemicals at PAH-impacted sites, and in addition provides more realistic estimates of risks/hazards posed by PAHs in soil with reduced uncertainty compared to estimates based on default RBAF and ABS.d values. Although default values are generally deemed acceptable by regulatory agencies, use of risk/hazard estimates based on these default values may compel insufficiently justified remedial action in some instances.

Organochlorine pesticides in the surrounding soils of POPs destruction facility: source fingerprinting, human health, and ecological risks assessment.

The elimination of persistent organic pollutants (POPs) obsolete pesticides stockpiles, particularly the organochlorine pesticides (OCPs), is one of the critical environmental issues faced by many developing countries. This pioneering study aimed to investigate the occurrence, source fingerprinting, human health, and ecological risks of OCPs in the surroundings of the lone POPs pesticide destruction facility in Pakistan. The ΣOCPs residual levels in soil ranged from 35.98 to 566.77ng/g dry weight (dw), with a mean concentration of 174.42+111.62ng/g (dw). The OCPs contamination levels in the soil followed the pattern as ΣHCHs > Σendrins > Σendosulfans > dieldrin > Σheptachlors > ΣDDTs > Σchlordanes > methoxychlor. The ΣHCHs residual concentrations were comparatively higher than the previous national and global soil studies. The recent accumulation of HCHs, DDTs, and heptachlor was observed in the study area as identified by β-HCH/∑HCHs, (DDE + DDD)/ΣDDTs, heptachlor/Σheptachlor, and heptachlor exo-epoxide/heptachlor ratios. The OCPs' lifetime carcinogenic risk through ingestion, dermal, and inhalation exposure routes ranged from 1.65E-08 to 2.91E-07, whereas the noncarcinogenic hazard quotient (HQ) ranged from 9.12E-05 to 1.61E-03. The risk vulnerability among age groups was in the order: adult > toddler > child > teen > infant. The calculated risk levels were within an acceptable limit of one in a million (1 × 10-6) for carcinogenic risk and HQ < 1 for noncarcinogenic risk. The current OCPs residual levels, especially dieldrin and endrin, exhibited low to medium ecological risks when compared to various worldwide limits. The upsurge of the OCPs' environmental contamination levels over the years and consideration of the food chain transfer might amplify the human health and ecological risks intensities.

Assessment for oil spill chemicals: Current knowledge, data gaps, and uncertainties addressing human physical health risk

Limited models are available to estimate human physical health risks (e.g., probability of outcomes such as lung disease, cancer, skin disease) from exposure to chemicals resulting from oil spills that may occur offshore and later impact coastline spills. An approach is presented to assess physical health risks from oil spills that involves establishing a platform capable of assessing aggregate health risk (via inhalation, ingestion, and dermal exposure routes). Gaps include the need to develop models reflecting oil spill concentration distributions given the influence from environmental, physical, biological and chemical factors. Human activities need to be quantified for different populations including emergency response workers, fishermen, shellfish consumers, and children who play at beaches that may be impacted by oil spills. Work is also needed in developing comprehensive toxicological profiles for the majority of chemicals - including dispersants found in oil spills - and to estimate toxicity from mixtures.