California Environmental Protection Agency Research Articles

Estimated mercury vapor exposure from amalgams among American pregnant women.

This study examined the impact of mercury (Hg) vapor exposure from amalgams among all American pregnant women. Amalgam-Hg vapor exposure among 1,665,890 weighted-pregnant women (n = 37) was examined in the 2015-2020 National Health and Nutrition Examination Survey (NHANES). Correlation coefficients between amalgam surfaces and daily micrograms (µg) of urinary Hg excretion and daily µg of Hg vapor exposure from amalgams per kilogram (Kg) bodyweight were calculated. Daily Hg vapor exposure from amalgams was compared to Hg vapor safety limits. About 600,000 pregnant women (∼36%) had at least one amalgam surface. Median daily urinary Hg excretion was ∼2.5-fold higher among pregnant women with amalgams as compared to pregnant women without amalgams. A significant correlation was observed between the number of amalgam surfaces and daily urinary Hg excretion. Among pregnant women with amalgams, it was estimated that the median daily Hg vapor dose from amalgams was 7.66 µg of Hg and 0.073 µg of Hg/Kg bodyweight. Among all pregnant women, ∼28% received daily Hg vapor doses from amalgams above the least restrictive United States (US) Environmental Protection Agency (EPA) safety limit and ∼36% received above the most restrictive California (CA) EPA safety limit. Given the potential for fetal toxicological effects from prenatal Hg vapor exposure, special emphasis needs to be placed on reducing/eliminating amalgams in pregnancy/women of reproductive age and future studies should evaluate adverse pregnancy outcomes.

Estimation of Serum PFOA Concentrations from Drinking and Non-Drinking Water Exposures.

Estimation of Serum PFOA Concentrations from Drinking and Non-Drinking Water Exposures.

Database examination, multivariate analysis, and machine learning: Predictions of vapor intrusion attenuation factors

Traditional soil vapor intrusion (VI) models usually rely on preset conceptual scenarios, simplifying the influences of limiting environmental covariates in determining indoor attenuation factors relative to subsurface sources. This study proposed a technical framework and applied it to predict VI attenuation factors based on site-specific parameters recorded in the United States Environmental Protection Agency (USEPA)’s and the California Environmental Protection Agency (CalEPA)’s VI databases, which can overcome the limitations of traditional VI models. We examined the databases with multivariate analysis of variance to identify effective covariates, which were then employed to develop VI models with three machine learning algorithms. The results of multivariate analysis show that the effective covariates include soil texture, source depth, foundation type, lateral separation, surface cover, and land use. Based on these covariates, the predicted attenuation factors by these new models are generally within one order of magnitude of the observations recorded in the databases. Then the developed models were employed to generate the generic indoor attenuation factors to subsurface vapor (i.e., the 95th percentile of selected dataset), the values of which are different between the USEPA’s and CalEPA’s databases by one order of magnitude, although comparable to recommendations by the USEPA and literature, respectively. Such a difference may reflect the significant regional disparity in factors such as building structures or operational conditions (e.g., indoor air exchange rates), which necessitates generating generic VI attenuation factors on a state-specific basis. This study provides an alternative for VI risk screens on a site-specific basis, especially in states with a good collection of datasets. Although the proposed technical framework is used for the VI databases, it can be equally applied to other environmental science problems.

Cancer Risk and Diesel Exhaust Exposure Among Railroad Workers

Inhalation exposure to diesel exhaust in the railroad work environment causes significant and quantifiable cancer risks to many railroad workers. Diesel exhaust has been identified as a known human carcinogen by the International Agency for Research on Cancer (“IARC”) and as a potential carcinogen by the United States Environmental Protection Agency (“USEPA”), the California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (“OEHHA”), and the National Institute for Occupational Safety & Health (“NIOSH”). Peer-reviewed literature defines the ambient air concentrations of diesel exhaust for several railroad occupations as being above environmental background levels. This study uses diesel exhaust concentrations in the railroad work environment in conjunction with the USEPA’s Integrated Risk Information System (“IRIS”) risk assessment methodology to quantify the cancer risk posed to railroad workers due to occupational inhalation exposure to diesel exhaust. NIOSH Bulletin 68 (2017) states that there is “no known safe level” of exposure to carcinogens and recommends an evaluation of the USEPA’s IRIS guidance to evaluate quantitative risk assessment of human exposure to occupational carcinogens. This is the first study to utilize USEPA methodology to calculate the excess lung cancer risk caused by railroad workers’ cumulative exposure to diesel exhaust.

More Pieces of the Puzzle: New Insights into Azoxystrobin Exposures and Neurotoxicity.

More Pieces of the Puzzle: New Insights into Azoxystrobin Exposures and Neurotoxicity.

Regional assessment of contaminant bioaccumulation in sport fish tissue in the Southern California Bight, USA

Marine recreational fisheries in California are economically and culturally important; however, consumption of contaminated seafood may be a human health risk. The California Environmental Protection Agency Office of Environmental Health Hazard Assessment developed Advisory Tissue Levels (ATLs) to be used in developing consumption recommendations protecting the health of fish consumers. This study characterizes extent and magnitude of bioaccumulation of contaminants in sport fish in Southern California relative to ATLs. Most zones exceeded the ATL for mercury corresponding to consumption of not more than 3 servings per week in one or more target species. A third of zones exceeded the ATL for total polychlorinated biphenyls (PCBs) corresponding to consumption of not more than 7 servings per week. However, neither mercury nor total PCBs exceeded the most restrictive, “do not consume”, thresholds in measured tissues. Contaminant concentrations in fish tissues have remained the same or decreased since a similar survey in 2009.

Health Effects of Naphthalene Exposure: A Systematic Evidence Map and Analysis of Potential Considerations for Dose-Response Evaluation.

Background:Naphthalene is a polycyclic aromatic hydrocarbon that has been associated with health effects, including cancer. As the state of the science on naphthalene toxicity continues to evolve, updated toxicity reference value(s) may be required to support human health risk assessment.Objectives:We present a systematic evidence map of studies that could be used to derive toxicity reference value(s) for naphthalene.Methods:Human and animal health effect studies and physiologically based pharmacokinetic (PBPK) models were identified from a literature search based on populations, exposures, comparators, and outcomes (PECO) criteria. Human and animal studies meeting PECO criteria were refined to a smaller subset considered most informative for deriving chronic reference value(s), which are preferred for assessing risk to the general public. This subset was evaluated for risk of bias and sensitivity, and the suitability of each study for dose–response analysis was qualitatively assessed. Lowest observed adverse effect levels (LOAELs) were extracted and summarized. Other potentially relevant studies (e.g., mechanistic and toxicokinetic studies) were tracked as supplemental information but not evaluated further. Existing reference values for naphthalene are also summarized.Results:We identified 26 epidemiology studies and 16 animal studies that were considered most informative for further analysis. Eleven PBPK models were identified. The available epidemiology studies generally had significant risk of bias and/or sensitivity concerns and were mostly found to have low suitability for dose–response analysis due to the nature of the exposure measurements. The animal studies had fewer risk of bias and sensitivity concerns and were mostly found to be suitable for dose–response analysis.Conclusion:Although both epidemiological and animal studies of naphthalene provide weight of evidence for hazard identification, the available animal studies appear more suitable for reference value derivation. PBPK models and mechanistic and toxicokinetic data can be applied to extrapolate these animal data to humans, considering mode of action and interspecies metabolic differences. https://doi.org/10.1289/EHP7381

Elemental composition of indoor and outdoor coarse particulate matter at an inner-city high school

Paired PM10 and fine particulate matter (PM2.5) samples were collected indoor and outdoor at a fully mechanically ventilated high school in the ultraindustrialized ship channel region of Houston, Texas over a two-month period. The primary foci of this research are to measure the elemental composition of ambient outdoor and indoor coarse particulate matter (PM10-2.5), characterize aerosol infiltration/ventilation, and obtain clues to their origins. Several metallic hazardous air pollutants were detected inside the school but at concentrations lower than even the most rigorous indoor air quality benchmarks. Only chromium may have potentially posed a hazard based on indoor air quality standards set by the California Environmental Protection Agency. Indoor-to-outdoor (I/O) mass abundance ratios for some metals (Li, Be, Si, Ti, Cr, Co, Ni, Zn, As, Se, Zr, Cd, Sn, Sb, Hf, and Pb) were significantly greater than 1 in PM10-2.5, suggesting corresponding indoor sources in the PM10-2.5 size range. Some other metals (Al, K, Ca, V, Mn, Fe, Cu, Ga, Rb, Sr, Y, Mo, Ce, Pr, Nd, Sm, Gd, Dy, Yb, and U) in PM10-2.5 had I/O ratios close to one suggesting they had predominantly outdoor origins. Enrichment factors of several metals including light rare earths (e.g. Cu, Sb, Pb, Mo, Cd, La, Ce, Pr, Nd, and Sm) with respect to local soil were overall the highest both indoors and outdoors, illustrating their anthropogenic origins. Several lines of evidence including light lanthanoid ratios, simultaneous La–Ce-Sm variations (ternary diagrams), and correlations with cracking catalysts indicated that petroleum refineries are principally responsible for the elevated lanthanoid concentrations. Rare earth element analysis revealed shifts between transient catalyst releases from petroleum refining operations and windblown soil resuspension as their dominant sources.

Determination and Risk Assessment of Heavy Metals Concentrations collected from Indoor houses at Lagos State of Nigeria

The aim of this study is to determine the levels of selected heavy metals (As, Pb, Zn, Cu and Cr) at 60 homes from the 20 local governments in Lagos State, Nigeria. Approval was sought from respective residential landlords and occupants of the sampledcommunities. Three dust samples were collected from each local government. A total of 60 dust samples were collected andlabelled according to the first three letters of each Local government. Indoor dust samples from households (furniture, containerbags, window slides, ceiling fan and standing fan) were collected using soft paint brushes. 0.5g of the homogenized mixture wasmeasured in triplicate labelled 1, 2 and 3 in different boiling tubes for digestion process. Each triplicate samples were digestedusing aqua regia for 1 hour at a temperature of about 100 degree celcius. Heavy metal concentrations were determined usingAgilent Technologies 4210 MP-AES Atomic Absorption Spectrometer (AAS). The concentration of heavy metals in the indoor dustwere dominated by Arsenic with an average concentration of 57.76-111.93 mg/kg followed Lead 13.81-116.60 mg/kg, Zinc 22.73-224.2 mg/kg, Copper 8.27-228.75 mg/kg and Chromium with concentration of 2.53-22.60 mg/kg respectively. The concentrationsof heavy metal in the areas investigated followed the order: Ar>Pb>Zn>Cu>Cr. The exposure dose was also estimated throughingestion, inhalation and dermal contacts, and the exposure route was highest for ingestion pathway. The health risk (carcinogenic and non-carcinogenic) of these heavy metals were assessed based on the United States Environmental ProtectionAgency health risk models. The estimated values were compared to standard guidelines and human health limits by the UnitedStates Environmental Protection Agency, USEPA and California Environmental Protection Agency, Ca/EPA. For noncarcinogenic risk, the hazard index values for all the studied metals were lower than the safe level of 1. The Total Lifetime Cancer Risk for adults and children were below the limit (1x10-6– 1x10-4) as standardized by USEPA except in children which was slightly higher than the permissible limit in two local government areas; (Shomolu L.G.A 1.03x10-4) and (Lagos Mainland 1.02x10-4). This indicates that the risk of carcinogenic effect occurring is likely in children with exposure to arsenic

Inhalation bioaccessibility of polycyclic aromatic hydrocarbons in heavy PM2.5 pollution days: Implications for public health risk assessment in northern China

Airborne (PM2.5) with aerodynamic diameter ≤ 2.5 μm was collected from 4 types of cities in northeast China during the heating period. The objectives of this study were to assess the concentrations variation of PM2.5-bound 12 carcinogenic polycyclic aromatic hydrocarbons (PAH12), to study the influence of simulated lung fluids on bioaccessibility of PAH12 and to estimate the variation of lifetime excess cancer risk to the residents, artificial lysosomal fluid (ALF) and Gamble’s solution were used. The number of lifetime excess cancer cases (determined by California Environmental Protection Agency method) as a result of PAH12 exposure (total concentration) was 4.00–430 (provincial central cities), 24.0–261 (energy-mining cities), 17.0–109 (forested city), and 20.0–69.0 (agricultural city) per million people, which relatively corresponded to a 92.2% and 96.2%, 92.6% and 97.3%, 92.2% and 94.2%, and 86.5% and 92.6% decrease after considering bioaccessibility following 24-h of Gamble’s solution and ALF extraction, respectively. Phenanthrene (Phe), dibenz[a,h]anthracene (DahA) and benzo[a]pyrene (BaP) were found to be the most bioaccessible types of PAH12 after the Gamble’s solution and ALF extraction in the PM2.5 samples from all the studied cities. Based on the point-estimate approach, short-term predictions of pulmonary toxicity caused by potential inhalation of airborne PM into the pulmonary system might be overestimated if bioaccessibility of PM2.5-bound PAH12 is not fully evaluated.

Atmospheric Pollution Characteristics and Inhalation Exposure Risk of Nitrated Polycyclic Aromatic Hydrocarbons in PM2.5 at the Ningdong Energy and Chemical Industry Base, Northwest China

Atmospheric PM2.5 samples were collected by using the active sampling method to investigate the pollution characteristics of nitrated polycyclic aromatic hydrocarbons (NPAHs) at the Ningdong Energy and Chemical Industry Base, Northwest China. Furthermore, the primary sources and the contributions of secondary formation sources as well as the inhalation exposure risks were identified. The main results were as follows. The concentration levels of ∑12NPAHs in PM2.5 ranged from 2.06 ng·m-3 to 37.14 ng·m-3 at the Ningdong Energy and Chemical Industry Base. The average concentrations of ∑12NPAHs were (25.57±5.76) ng·m-3 in winter and (6.22±1.74) ng·m-3 in summer for the Baofeng sampling site associated with the energy industry. The average concentrations of ∑12NPAHs were (7.13±1.44) ng·m-3 in winter and (2.58±0.39) ng·m-3 in summer for the Yinglite sampling site associated with chemical and electricity industries. The levels of ∑12NPAHs in PM2.5 were higher in winter than those in summer because of the increased heating in winter. Atmospheric pollution levels of NPAHs at the Baofeng sampling site were generally higher than those at the Yinglite sampling because of the higher primary NPAHs emissions from coal mining and coke production in Baofeng compared with those from the chemical industry in Yinglite. The calculated nocturnal/diurnal ratios revealed that the concentrations of ∑12NPAHs in PM2.5 during the summer season were higher in the daytime than those in the nighttime, but the opposite trend occurred in winter, thus indicating that secondary formation processes made more contributions to NPAHs during summer in the daytime. The congener profiles of NPAHs were mainly composed of primary emission markers such as 2-nitrofluorene (2N-FLO) and 6-nitrochrysene (6N-CHR), which were the predominant ones in winter and summer for both the Baofeng and Yinglite sampling sites. Total proportions of 2N-FLO and 6N-CHR were 46% in winter and 73% in summer for Baofeng and 59% in winter and 55% in summer for Yinglite, respectively. Meanwhile, 3N-PHE, which is a marker compound of secondary formation processes, accounted for a higher percentage in summer especially at Yinglite. This finding revealed that the chemical production at Yinglite was associated with higher precursor emissions than that of Baofeng, and thus, more NPAHs were derived from secondary formation processes. Moreover, ∑12NPAHs/∑16PAHs ratios were calculated to identify the potential sources of NPAHs across the city. The results indicated that higher environmental temperatures in summer promoted the degradation of PAHs and secondary formation of NPAHs, and thus, secondary formation contributed more to NPAHs in summer than in winter. Furthermore, lung cancer risks induced by inhalation exposures to ∑5NPAHs were assessed based on the BaP equivalent toxicity factor. The results showed that the lung cancer risk values of ∑5NPAHs were (3.06×10-5±1.36×10-5) in winter and (1.79×10-5±0.80×10-5) in summer for the Baofeng sampling site, while the risk values were (2.85×10-5±1.20×10-5) in winter and (1.86×10-5±0.83×10-5) in summer for the Yinglite sampling site. Notably, the lung cancer risk values in our study for both sampling sites were higher than the standard limit value (1.00×10-5) of the California Environmental Protection Agency, which indicates that the local population at the Ningdong Energy and Chemical Industry Base has been subjected to potentially elevated lung cancer risks due to inhalation exposures to PM2.5-bound NPAHs.

California to ban chlorpyrifos

California is slated to become the third US state to ban the organophosphate insecticide chlorpyrifos, following action in Hawaii and New York. California’s Department of Pesticide Regulation (DPR) has initiated the process of canceling all uses of the pesticide in the state to protect farmworkers, children, and the environment, the California Environmental Protection Agency (CalEPA) announced on May 8. Chlorpyrifos is associated with neurodevelopmental problems and impaired brain function in children. Earlier this year, California listed chlorpyrifos as a toxic air contaminant. The state is therefore required to establish measures to protect farmworkers and other people who are likely to be exposed to the pesticide. The state determined that sufficient control measures are not feasible, so it is now proceeding with a ban on the chemical. The process is likely to take up to 2 years, according to the CalEPA. “California’s action to cancel the registration of chlorpyrifos is needed

Revisiting environmental inequity in Southern California: Does environmental risk increase in ethnically homogeneous or mixed communities?

This study revisits the concept of environmental inequity in Southern California using the California Environmental Protection Agency’s most recent data and spatial models. Empirical studies in the...

The Emergence and Divergence in Performance: Management Systems in California State Government

An understudied aspect of performance management systems is how performance management systems emerge in public agencies. This research focuses on the emergence of performance management systems, studying two cases with divergent outcomes in the State of California. The first case study is about the Performance Management Council, which included the voluntary participation of more than 20 California state agencies, departments, and divisions. The second case study is about the Department of Toxic Substances Control within the California Environmental Protection Agency. These cases, which impacted 35 million residents in a state with a $200 billion annual budget, potentially offer findings valuable to nations and to large sub-national units of government such as large states, districts, and provinces. This research offers three contributions to public sector performance management research literature. First, it addresses a gap in the understanding of how performance management systems emerge through dialogue and learning forums. Second, the research extends the study of performance management to the policy arenas of environmental protection, water resources, and other policy domains typically not researched in performance management. Third, the research connects performance management to the research on the reform of public agencies, diffusion of practices, and organizational change.

Pollution characteristics of ambient PM2.5–bound benzo[a]pyrene and its cancer risks in Beijing

The purpose of this study was to reveal the pollution characteristics of ambient PM2.5–bound benzo[a]pyrene (B[a]P) in Beijing and to assess the lifetime cancer risk from respiratory pathway exposure. The average daily dose was evaluated by the annual concentrations of ambient PM2.5–bound B[a]P, combined with Chinese human exposure factors and the age sensitivity factors. The 70-year lifetime cancer risks of different groups were assessed by the exposure assessment and stochastic analysis method recommended by California Environmental Protection Agency. The groups were divided by age and gender. The results showed that the ambient PM2.5–bound B[a]P concentration during the cold season was 15.7 times greater than that during the warm season in Beijing. The annual average concentrations of PM2.5–bound B[a]P in outdoors and indoors were 1.67 ng/m3 and 1.04 ng/m3, respectively, which exceeded the limit of Chinese National Ambient Air Quality Standard. The cancer risks of PM2.5–bound B[a]P in males, females, and the general population were 9.085 × 10−6, 8.050 × 10−6, and 8.740 × 10−6, respectively. The cancer risk constituent ratios of ambient PM2.5–bound B[a]P in early life (≤16 years of age) for males, females, and the general population were 70.9%, 71.4%, and 71.3%, respectively. The males' cancer risk of PM2.5–bound B[a]P in Beijing was higher than that of the females. The early life cancer risk exposure to PM2.5–bound B[a]P should be paid more attention.

California Synthetic Turf Study

There are over 900 synthetic turf sport fields in California (CA). Public concern about cancer incidents among young athletes, especially soccer goalies, has increased in recent years. The Office of Environmental Health Hazard Assessment of the California Environmental Protection Agency has launched a 4-year environmental health study of the potential health effects associated with synthetic turf fields and playground mats containing recycled tires (i.e., crumb rubber). The aims of the study are to: 1) identify and characterize chemicals and particles released from these fields and playgrounds; 2) evaluate potential human exposures during use of such fields or playgrounds; and 3) assess human health risk from the exposures. The chemical/particle characterization included preinstalled crumb rubber from recyclers, installed crumb rubber from fields, concentrations in air above fields, and targeted laboratory chamber tests. Crumb rubber was sampled from four CA recyclers for initial chemical characterization. A stratified random sampling scheme was applied to recruit fields in various climate regions across CA where infield crumb was sampled. A subset of the fields (n = 35) were included in the detailed environmental exposure testing with both on-field and off-field monitoring. Players performed scripted soccer activities near the on-field monitoring area and testing was conducted both with and without activity on the field. Monitoring was conducted at 1 off-field location and 3 on-field locations near (and downwind from) the active zone and at up to 5 elevations above the field. Monitoring included particulate matter (PM) measurements (number of particles ranging 7 nm to 20 µm; mass of PM2.5 and PM10), metals, volatile and semi-volatile organic chemicals, ozone, temperature (subsurface, surface and above the field), light intensity, humidity and wind speed/direction. This presentation will describe the study protocol and summarize the preliminary data.

Environmental Inequities and Water Policy During a Drought: Burdened Communities, Minority Residents, and Cutback Assignments

AbstractIn 2014 the California Environmental Protection Agency (CalEPA) released CalEnviroScreen 2.0, developed to identify communities facing “multiple burdens of pollution and socioeconomic disadvantage” (CalEnviroScreen FAQs, 2016). Contemporaneously, California was suffering a severe drought. CalEPA implemented emergency water cutbacks such that community allowances ranged from approximately 70%–430% of the U.S. average for water consumption. Decades of research find that racial and ethnic minorities face greater environmental burdens than others. Did the CalEPA cutbacks disproportionately affect already burdened communities or those with higher percentages of minorities? Using geographic information systems and spatial regression analysis, we find that the water cutbacks did not, ceteris paribus, further stress already burdened communities, but communities with a more significant percentage of Hispanics are estimated to receive lower water allowances even controlling for poverty. This research broadens the areas in which we can look for environmental (in)justice beyond standard dis/amenities, and implies that even intra‐organizational policy goals of reducing environmental justice burdens may not be enough.

A multivariate analysis of CalEnviroScreen: comparing environmental and socioeconomic stressors versus chronic disease

BackgroundThe health-risk assessment paradigm is shifting from single stressor evaluation towards cumulative assessments of multiple stressors. Recent efforts to develop broad-scale public health hazard datasets provide an opportunity to develop and evaluate multiple exposure hazards in combination.MethodsWe performed a multivariate study of the spatial relationship between 12 indicators of environmental hazard, 5 indicators of socioeconomic hardship, and 3 health outcomes. Indicators were obtained from CalEnviroScreen (version 3.0), a publicly available environmental justice screening tool developed by the State of California Environmental Protection Agency. The indicators were compared to the total rate of hospitalization for 14 ICD-9 disease categories (a measure of disease burden) at the zip code tabulation area population level. We performed principal component analysis to visualize and reduce the CalEnviroScreen data and spatial autoregression to evaluate associations with disease burden.ResultsCalEnviroScreen was strongly associated with the first principal component (PC) from a principal component analysis (PCA) of all 20 variables (Spearman ρ = 0.95). In a PCA of the 12 environmental variables, two PC axes explained 43% of variance, with the first axis indicating industrial activity and air pollution, and the second associated with ground-level ozone, drinking water contamination and PM2.5. Mass of pesticides used in agriculture was poorly or negatively correlated with all other environmental indicators, and with the CalEnviroScreen calculation method, suggesting a limited ability of the method to capture agricultural exposures. In a PCA of the 5 socioeconomic variables, the first PC explained 66% of variance, representing overall socioeconomic hardship. In simultaneous autoregressive models, the first environmental and socioeconomic PCs were both significantly associated with the disease burden measure, but more model variation was explained by the socioeconomic PCs.ConclusionsThis study supports the use of CalEnviroScreen for its intended purpose of screening California regions for areas with high environmental exposure and population vulnerability. Study results further suggest a hypothesis that, compared to environmental pollutant exposure, socioeconomic status has greater impact on overall burden of disease.

Brief Introduction of Pollution Sites Remediation and Risk Assessment and Its Policy Making in United States

Site remediation has become an imperative part of environmental protection in China due to recent economic development, urban spreading, new industries replacing old ones, relocation of old industrial sites, and increased environmental conscience. This paper mainly introduced the concept, method, calculation, risk assessment and management for polluted sites remediation based on experience from California, USA. Further, the paper presented the concept of vapor intrusion and how to use vapor intrusion methodology to determine site remediation standard. Mathematical modeling approaches were also discussed in terms of how to determine the residual pollutant concentrations in soil and how to calculate indoor vapor concentrations. Based on risk assessment, California Environmental Protection Agency, Water Resources Control Board issued a 'Low Threat Underground Storage Tank Case Closure Policy' for impacted underground storage tank sites. The numerical criteria in the Policy were based on calculations of human health risk assessment. Finally, a real case study in California, USA, was presented to demonstrate how the risk assessment calculations were applied in polluted site remediation, which helps to answer the question of 'how clean is clean'.

Dynamic single-interface hollow fiber liquid phase microextraction of Cr(VI) using ionic liquid containing supported liquid membrane

The concept of dynamic single-interface hollow fiber membrane liquid-phase microextraction (HF-LPME), where the target analyte was extracted on-line and eluted inside the lumen of the HF membrane, was explored. An ionic liquid containing supported liquid membrane was used for the trace determination of Cr(VI) as a model compound. Since the extraction took place on-line inside the hollow fiber membrane, the mass transfer behavior was described and discussed in comparison with the conventional HF-LPME. The extraction efficiency was improved by a recirculation configuration of the sample solution at relatively high sampling flow rates as a result of the increased effective contact area. The positive pressure observed to be built up during extraction was overcome by a flow-balancing pressure design. The dynamic single-interface HF-LPME method with an enrichment factor of 41, a detection limit of 1.2µgL−1 and determination limit of 4.0µgL−1 was successfully applied to the reliable determination of Cr(VI) from environmental water samples. The quantification limit is below the maximum contaminant level in drinking water, set at 10µgL−1 of hexavalent chromium by the California Environmental Protection Agency.