EPA's Database Research Articles

The Application of Liquid Chromatography for the Analysis of Organic UV Filters in Environmental and Marine Biota Matrices

Sunscreens are topical preparations containing one or more compounds that protect humans from ultraviolet (UV) light. This review focuses on analytical methods, particularly liquid chromatography, with the aim of identifying and determining UV filters (UVFs) in environmental and marine biota matrices. A literature review was conducted using NIH (PubMed and Medline), FDA and EPA databases, Google Scholar, and federal regulations. This retrospective literature review is focused on the last five years. UVF quantification in environmental and biological matrices showed a wide array of methods where liquid chromatography is predominant. The scientific literature identified a large variety of analytical methodologies that are compared in this review to evaluate the better results in terms of limits of quantification and the possibility to identify as many analytes as possible simultaneously.

414 Housing and Environmental Exposures: A Systematic Literature Review on Research and Policy Implications

OBJECTIVES/GOALS: Poor housing conditions and quality can be linked with residents’environmental exposures, which may contribute to a variety of adverse health outcomes. This systematic literature review will examine literature around housing, environmental exposure, and health; and policy implications to reduce the impact of housing on environmental exposures. METHODS/STUDY POPULATION: This systematic literature review will identify and evaluate published peer-reviewed articles as well as governmental and NGO policy briefs relating to connections between housing quality and condition, neighborhood characteristics, and environmental exposures (e.g., lead poisoning, secondhand smoke, PFAS chemicals) in the United States; and will particularly focus on health implications of such environmental exposures, racial/ethnic and socioeconomic disparities in exposure, and current and future policy recommendations to alleviate the association between housing and environmental risk. A computerized literature search of relevant electronic databases (e.g., PubMed, Sociological Abstracts, EPA database, Congressional database) for literature published after 2000 will be conducted. RESULTS/ANTICIPATED RESULTS: The findings from this literature review will be split up into categorizations around (1) the contribution of housing/neighborhoods on resident environmental exposure; (2) geospatial and demographic inequality (historic and current) around housing/neighborhood conditions contributing to disproportionate environmental exposures for low-income and minoritized residents; (3) health implications of environmental exposures; (4) prior policy addressing the connections between housing/neighborhoods and environmental risk; and (5) future policy recommendations to improve housing/neighborhood quality and minimize environmental exposures for residents. DISCUSSION/SIGNIFICANCE: This project will illuminate connections between housing conditions and environmental exposures, health implications of these exposures, and contribute to advancing understanding of potential policies to reduce adverse environmental health impacts of poor housing conditions for residents (particularly for low-income, minoritized groups).

Diisocyanates influence models of atopic dermatitis through direct activation of TRPA1.

We recently used EPA databases to identify that isocyanates, most notably toluene diisocyanate (TDI), were the pollutant class with the strongest spatiotemporal and epidemiologic association with atopic dermatitis (AD). Our findings demonstrated that isocyanates like TDI disrupted lipid homeostasis and modeled benefit in commensal bacteria like Roseomonas mucosa through disrupting nitrogen fixation. However, TDI has also been established to activate transient receptor potential ankyrin 1 (TRPA1) in mice and thus could directly contribute to AD through induction of itch, rash, and psychological stress. Using cell culture and mouse models, we now demonstrate that TDI induced skin inflammation in mice as well as calcium influx in human neurons; each of these findings were dependent on TRPA1. Furthermore, TRPA1 blockade synergized with R. mucosa treatment in mice to improve TDI-independent models of AD. Finally, we show that the cellular effects of TRPA1 are related to shifting the balance of the tyrosine metabolites epinephrine and dopamine. This work provides added insight into the potential role, and therapeutic potential, or TRPA1 in the pathogenesis of AD.

Exposure to isocyanates predicts atopic dermatitis prevalence and disrupts therapeutic pathways in commensal bacteria

Atopic dermatitis (AD) is a chronic inflammatory skin condition increasing in industrial nations at a pace that suggests environmental drivers. We hypothesize that the dysbiosis associated with AD may signal microbial adaptations to modern pollutants. Having previously modeled the benefits of health-associated Roseomonas mucosa, we now show that R. mucosa fixes nitrogen in the production of protective glycerolipids and their ceramide by-products. Screening EPA databases against the clinical visit rates identified diisocyanates as the strongest predictor of AD. Diisocyanates disrupted the production of beneficial lipids and therapeutic modeling for isolates of R. mucosa as well as commensal Staphylococcus. Last, while topical R. mucosa failed to meet commercial end points in a placebo-controlled trial, the subgroup who completed the full protocol demonstrated sustained, clinically modest, but statistically significant clinical improvements that differed by study site diisocyanate levels. Therefore, diisocyanates show temporospatial and epidemiological association with AD while also inducing eczematous dysbiosis.

Environmental impact assessment of hydrogen production via steam methane reforming based on emissions data

Steam methane reforming (SMR) using natural gas is the most commonly used technology for hydrogen production. Industrial hydrogen production contributes to pollutant emissions, which may differ from the theoretical estimates due to process conditions, type and state of installed pollution control equipment. The aim of this study was to estimate the impacts of hydrogen production using facility-level real emissions data collected from multiple US EPA databases. The study applied the ReCiPe2016 impact assessment method and considered 12 midpoint and 14 endpoint impacts for 33 US SMR hydrogen production facilities. Global warming impacts were mostly driven by CO2 emissions and contributed to 94.6% of the endpoint impacts on human health, while global warming impact on terrestrial ecosystems contributed to 98.3% of the total endpoint impacts on ecosystems. The impacts estimated by direct emissions from the 33 facilities were 9.35 kg CO2e/kg H2 which increased to 11.2 kg CO2e/kg H2 when the full life cycle of hydrogen production including upstream emissions was included. The average global warming impact could be reduced by 5.9% and 11.1% with increases in hydrogen production efficiency by 5% and 10%, respectively. Potential impact reductions are also found when natural gas hydrogen production feedstock is replaced by renewable sources, with the greatest reduction of 78.1% found in hydrogen production via biomass gasification, followed by 68.2% reduction in landfill gas and 53.7% reduction in biomethane-derived hydrogen production.

An EPA database on the effects of engineered nanomaterials-NaKnowBase

The US EPA Office of Research and Development (ORD) has conducted a research program assessing potential risks of emerging materials and technologies, including engineered nanomaterials (ENM). As a component of that program, a nanomaterial knowledge base, termed “NaKnowBase”, was developed containing the results of published ORD research relevant to the potential environmental and biological actions of ENM. The experimental data address issues such as ENM release into the environment; fate, transport and transformations in environmental media; exposure to ecological species or humans; and the potential for effects on those species. The database captures information on the physicochemical properties of ENM tested, assays performed and their parameters, and the results obtained. NaKnowBase (NKB) is a relational SQL database, and may be queried either with SQL code or through a user-friendly web interface. Filtered results may be output in spreadsheet format for subsequent user-defined analyses. Potential uses of the data might include input to quantitative structure-activity relationships (QSAR), meta-analyses, or other investigative approaches.

Clinical decision support in a hospital electronic prescribing system informed by local data: experience at a tertiary New Zealand centre.

An electronic prescribing and administration (ePA) system has been progressively rolled out to Canterbury District Health Board (CDHB, Christchurch, New Zealand) public hospitals since 2014, and is currently used for around 1300 tertiary beds. ePA data can be used to monitor user behaviour, and to evaluate and inform the local customisation of clinical decision support (CDS) tools within the ePA system. To describe retrospectively illustrative vignettes of CDHB ePA analyses that have been used for CDS. Alerts were developed according to a set of common principles agreed upon by the CDHB CDS Working Group. Alerts were informed and evaluated by extracting and parsing data for various time periods during 2016 to 2018 from the CDHB ePA database. There was a median of 74 000 prescriptions a month. After examining 525 spironolactone prescriptions, the high dose alert threshold was set at 100 mg with an expected alert burden of 3%. The presence of a ceftriaxone shortage prescribing alert for 1 week was associated with a prescribing rate that was lower than 95% of the preceding 52 weeks. Following review of 367 fentanyl patch alerts, revision of the alert led to false positives falling from 43% to 3% (P < 0.0001). At the point of firing, 6% of antithrombotic drug interactions alerts led to immediate changes in prescriptions (94% overridden), and a further 22% were changed within 30 min after the alert. Local data extracts from ePA systems can inform iterative configuration of the software and monitor user behaviour.

A systematic analysis of the overall nutritional contribution of food loss and waste in tomatoes, spinach, and kidney beans as a function of processing

AbstractDeveloping more nutrient‐rich, sustainable food supply chains aligns with the co‐benefits of tackling malnutrition and minimizing food loss and waste. While food waste and nutrient loss as a function of food waste and processing have separately been a topic of much previous research, nutrient loss as a function of both processing and food waste from farm to fork has not been addressed. This critical analysis was motivated by the: challenge of nourishing a growing population, the economic impact of food waste, the societal costs of malnutrition, and the overall need to extend produce shelf life sustainably. Both food and nutrient loss and waste can occur simultaneously at various levels throughout the value chain as a function of different processing methods. Combined effects of food waste and nutrient availability/losses were determined through a systematic analysis of the available peer‐reviewed research data during thermal, nonthermal, and minimal processing for tomatoes, spinach, and kidney beans. The waste and loss datasets were derived from the USDA, the FAO, and the US EPA databases. This work presents a justification for more research to reduce nutrient loss and food waste to obtain a more sustainable supply of nutrients in the food industry.Practical ApplicationsThis analysis serves as a guide for food industry stakeholders concerned with nutrient retention as a result of processing and food waste in the food value chain. It also assesses the combined impact of processing and food waste on nutrient loss from farm to fork. Available nutrient retention data as a function of retort, microwave, high pressure, aseptic and fresh processing, and food waste were employed. To our knowledge, there has not been a study on food waste as a function of processing that considers nutrient retention and loss as a function of food waste within the entire value chain. A summary of specific research needs for a holistic view on nutrient retention affecting product, process, and package conditions through the value chain was presented.

Sunscreens: UV filters to protect us: Part 2-Increasing awareness of UV filters and their potential toxicities to us and our environment.

BackgroundSunscreens are topical preparations containing one or more compounds that filter, block, reflect, scatter, or absorb ultraviolet (UV) light. Part 2 of this review focuses on the environmental, ecological effects and human toxicities that have been attributed to UV filters.MethodsLiterature review using NIH databases (eg, PubMed and Medline), FDA and EPA databases, Google Scholar, the Federal Register, and the Code of Federal Regulations (CFR).LimitationsThis was a retrospective literature review that involved many different types of studies across a variety of species. Comparison between reports is limited by variations in methodology and criteria for toxicity.ConclusionsIn vivo and in vitro studies on the environmental and biological effects of UV filters show a wide array of unanticipated adverse effects on the environment and exposed organisms. Coral bleaching receives considerable attention from the lay press, but the scientific literature identifies potential toxicities of endocrine, neurologic, neoplastic and developmental pathways. These effects harm a vast array of aquatic and marine biota, while almost no data supports human toxicity at currently used quantities (with the exception of contact allergy). Much of these data are from experimental studies or field observations; more controlled environmental studies and long-term human use data are limited. Several jurisdictions have prohibited specific UV filters, but this does not adequately address the dichotomy of the benefits of photoprotection vs lack of eco-friendly, safe, and FDA-approved alternatives.

Modeling capillary fringe effect on petroleum vapor intrusion from groundwater contamination

At contaminated sites, indoor inhalation of volatile organic compounds from groundwater contamination, known as vapor intrusion (VI), is an important exposure pathway to determine groundwater cleanup level. Based on empirical analysis, US EPA concluded that there is a low probability for vapors from fuel hydrocarbons dissolved in groundwater to induce indoor concentrations that exceed risk-based standards, and recommended 6 feet vertical building-source separation distance as the risk screening tool for such cases. In this study, we examine this recommendation by performing numerical modeling to investigate the detailed effects of the capillary fringe on petroleum vapor biodegradation and attenuation. First, the numerical model is validated by comparison with laboratory data and field measurements in US EPA's database. Then the verified model is used to simulate two scenarios involving the capillary fringe effect, one with a groundwater source at various depth and the other with a soil gas source located above the groundwater level. For a groundwater contaminant source, the capillary fringe plays a significant role in VI by controlling the soil moisture content and oxygen availability, thus affecting the soil gas concentration biodegradation and attenuation. Specifically, the capillary fringe effect can significantly decrease the indoor air concentration by decreasing upward diffusion rates of hydrocarbon, increasing the thickness of the aerobic zone, and enhancing aerobic biodegradation. As a result, it is highly unlikely for sources located at groundwater level to induce unacceptable vapor intrusion risks, supporting US EPA's recommendation. Moreover, the simulations suggest that the vertical smear zone of residual light non-aqueous liquid contamination, induced by temporal fluctuations of groundwater level, may lead to a potential threat to indoor air quality for a short vertical source-building separation distance, and thus requires more attention. The sensitivity test of the numerical model also indicates that it is the vertical separation distance between building foundation and the top of the smear zone instead of the smear zone thickness that should be given more attention during the investigation.

Evaluation of potential carcinogenicity of organic chemicals in synthetic turf crumb rubber

Currently, there are >11,000 synthetic turf athletic fields in the United States and >13,000 in Europe. Concerns have been raised about exposure to carcinogenic chemicals resulting from contact with synthetic turf fields, particularly the infill material (“crumb rubber”), which is commonly fabricated from recycled tires. However, exposure data are scant, and the limited existing exposure studies have focused on a small subset of crumb rubber components. Our objective was to evaluate the carcinogenic potential of a broad range of chemical components of crumb rubber infill using computational toxicology and regulatory agency classifications from the United States Environmental Protection Agency (US EPA) and European Chemicals Agency (ECHA) to inform future exposure studies and risk analyses. Through a literature review, we identified 306 chemical constituents of crumb rubber infill from 20 publications. Utilizing ADMET Predictor™, a computational program to predict carcinogenicity and genotoxicity, 197 of the identified 306 chemicals met our a priori carcinogenicity criteria. Of these, 52 chemicals were also classified as known, presumed or suspected carcinogens by the US EPA and ECHA. Of the remaining 109 chemicals which were not predicted to be carcinogenic by our computational toxicology analysis, only 6 chemicals were classified as presumed or suspected human carcinogens by US EPA or ECHA. Importantly, the majority of crumb rubber constituents were not listed in the US EPA (n = 207) and ECHA (n = 262) databases, likely due to an absence of evaluation or insufficient information for a reliable carcinogenicity classification. By employing a cancer hazard scoring system to the chemicals which were predicted and classified by the computational analysis and government databases, several high priority carcinogens were identified, including benzene, benzidine, benzo(a)pyrene, trichloroethylene and vinyl chloride. Our findings demonstrate that computational toxicology assessment in conjunction with government classifications can be used to prioritize hazardous chemicals for future exposure monitoring studies for users of synthetic turf fields. This approach could be extended to other compounds or toxicity endpoints.

Residential inter-zonal ventilation rates for exposure modeling

ABSTRACTResidential inter-zonal (e.g., between rooms) ventilation is comprised of fresh air infiltration in and exfiltration out of the whole house plus the “fresh” air that is entering (and exiting) the room of interest from other rooms or areas within the house. Clearly, the inter-zone ventilation rate in any room of interest will be greater than the infiltration/exfiltration ventilation rate of outdoor air for the whole house. The purpose of this study is to determine how much greater the inter-zonal ventilation rate is in typical U.S. residences compared to the whole house ventilation rate from outdoor air. The data for this statistical analysis came from HouseDB, a 1995 EPA database of residential ventilation rates. Analytical results indicate that a lognormal distribution provides the best fit to the data. Lognormal probability distribution functions (PDFs) are provided for various inter-zonal ventilation rates for comparison to the PDF for the whole house ventilation rates. All ventilation rates are expressed as air change rates per hour (ACH). These PDFs can be used as inputs to exposure models. This analysis suggests that if one were performing a deterministic analysis for unknown housing stocks in the U.S., a default mean and median ACH values of 0.4/hr and 0.3/hr, respectively, for whole house ventilation would be appropriate; and 0.7/hr and 0.6/hr, respectively, for inter-zonal ventilation.

Ideology vs. Interest Group Politics in U.S. Energy Policy

The political economy of energy policy in the United States is dominated by a combination of ideological partisanship and interest group lobbying. Both are reflected in the widespread belief that, under the Obama administration, the Environmental Protection Agency (“EPA”) was engaged in a misguided “war on coal,” despite the coal industry’s status as the leading industrial source of air pollution and compelling evidence that the benefits of EPA’s regulations vastly exceed their costs. This conflict is persistent and unresolved, notwithstanding repeated involvement of the Supreme Court over the last few years. The politics of this conflict are compounded by tensions between electricity managers and environmental regulators. Much of this tension is driven by competing perspectives: EPA’s focus has been on the national costs and benefits of its rules, whereas grid managers operate regionally. This Article resolves the apparent conflicts by downscaling the regulatory analyses of three highprofile (and highly litigated) EPA rules addressing emissions of conventional pollutants, air toxics, and greenhouse gases associated with climate change from coal-fired power plants. This Article utilizes complementary EPA databases and draws on several model estimates to examine the regional impacts— both costs and benefits—of regulations targeting coal-fired power plants. Overall, this Article finds that the distribution of both the compliance costs and environmental benefits of the rules are roughly commensurate with each region’s reliance on coal-fired power plants, particularly older facilities. That is, the benefits of reducing emissions under these rules are predominantly local. As a consequence, regulatory benefits exceed costs not only at the national level but at the regional level as well, and typically by large margins. Further, with a few important caveats, we find that while the EPA rules will hasten power plant closures, most will occur in electricity markets that have sufficient excess capacity to mitigate potential threats to electricity supplies and reliability. Nevertheless, opposition to the rules persists, which we explain as the product of a combination of both interest group and ideological/partisan opposition. Interestingly, ideological/ partisan opposition appears to hold greater sway based on varying levels of political opposition regionally and may— incrementally—be shifting in EPA’s favor.

Variation in predicted internal concentrations in relation to PBPK model complexity for rainbow trout

The present study is motivated by the increasing demand to consider internal partitioning into tissues instead of exposure concentrations for the environmental toxicity assessment. To this end, physiologically based pharmacokinetic (PBPK) models can be applied. We evaluated the variation in accuracy of PBPK model outcomes depending on tissue constituents modeled as sorptive phases and chemical distribution tendencies addressed by molecular descriptors. The model performance was examined using data from 150 experiments for 28 chemicals collected from US EPA databases. The simplest PBPK model is based on the “Kow-lipid content” approach as being traditional for environmental toxicology. The most elaborated one considers five biological sorptive phases (polar and non-polar lipids, water, albumin and the remaining proteins) and makes use of LSER (linear solvation energy relationship) parameters to describe the compound partitioning behavior. The “Kow-lipid content”-based PBPK model shows more than one order of magnitude difference in predicted and measured values for 37% of the studied exposure experiments while for the most elaborated model this happens only for 7%. It is shown that further improvements could be achieved by introducing corrections for metabolic biotransformation and compound transmission hindrance through a cellular membrane. The analysis of the interface distribution tendencies shows that polar tissue constituents, namely water, polar lipids and proteins, play an important role in the accumulation behavior of polar compounds with H-bond donating functional groups. For compounds without H-bond donating fragments preferable accumulation phases are storage lipids and water depending on compound polarity.

Vapor intrusion attenuation factors relative to subslab and source, reconsidered in light of background data

The basis upon which recommended attenuation factors for vapor intrusion (VI) have been derived are reconsidered. By making a fitting curve to the plot showing the dependence of observed indoor air concentration (c(in)) on subslab concentration (c(ss)) for residences in EPA database, an analytical equation is obtained to identify the relationship among c(in), css and the averaged background level. The new relationship indicates that subslab measurements may serve as a useful guide only if c(ss) is above 500 μg/m(3). Otherwise, c(in) is independent of c(ss), with a distribution in good agreements with other studies of background levels. Therefore, employing this screening value (500 μg/m(3)), new contaminant concentration attenuation factors are proposed for VI, and the values for groundwater-to-indoor and subslab-to-indoor air concentration attenuation factors are 0.004 and 0.02, respectively. The former is applied to examining the reported temporal variations of c(in) obtained during a long-term monitoring study. The results show that using this new groundwater-to-indoor air concentration attenuation factor also provides a reasonably conservative estimate of c(in).

Do national advisories serve local consumers: an assessment of mercury in economically important North Carolina fish

Consumption of marine fish provides both benefits (lean protein, omega-3 fatty acids and essential nutrients) and risks (main source of mercury (Hg) exposure for humans). Mercury is a potent neurotoxin and the source of more fish advisories nationwide than any other toxicant. Despite the widespread nature of Hg, it is unknown whether local Hg contamination reflects national and regional levels often used as bases to inform consumers of potential fish consumption risk. Thus, the objectives of our study were to examine Hg levels of six commonly consumed marine species harvested locally off the North Carolina coast and to compare our results to published regional (Monterey Bay Aquarium's Seafood Watch List) and national (Environmental Protection Agency, EPA, and Food and Drug Administration, FDA) Hg averages, action levels, and guidelines. We found significant differences in Hg concentrations among collected species, and we identified correlations between Hg concentration and fish length and trophic levels. Collected mahi mahi and triggerfish were below the EPA fish tissue action level (0.3ppm). Wahoo and grouper exceeded the EPA action level but were below the FDA action level (1.0ppm). King mackerel had the highest Hg concentration among targeted species, exceeding both EPA and FDA action levels. Further, our local results were not always consistent with calculated averages from EPA and FDA databases for the same species, and although many of our findings were consistent with Monterey Bay Aquarium's Seafood Watch List (southeast region), recommendations based on Hg levels would conflict with recommendations they provide based on sustainability. We find regional and national averages are not always reflective of local Hg contamination and suggest local data may be needed to accurately assess consumer risk.

CHEMICAL ASSESSMENT CHANGES

TWO CONTROVERSIAL Bush Administration policies affecting assessments of chemical risks and air-quality standards have been overturned by EPA Administrator Lisa P. Jackson. Late last month, Jackson implemented a new policy designed to increase the scientific integrity of an EPA database called the Integrated Risk Information System. IRIS contains scientific judgments from EPA on the safe daily dose of more than 500 chemicals. Regulators from around the world rely on the database when making decisions that have significant financial impact, such as the degree of cleanup a polluter must undertake at a contaminated site and how much human exposure to a chemical is allowable. The Bush Administration’s IRIS policy, unveiled last year, gave federal polluters, notably the Departments of Defense and Energy, more sway over EPA’s chemical risk assessments (C&EN, April 21, 2008, page 9). The Government Accountability Office, the investigative arm of Congress, strongly criticized the Bush Administration’s move, saying...

Identifying Likely PM2.5 Sources on Days of Elevated Concentration: A Simple Statistical Approach

A simple statistical method is described for identifying the likely importance of local sources of PM2.5 in a region on days when the National Ambient Air Quality Standard is exceeded. The method requires only PM2.5 mass concentration and wind direction data, and makes use of the EPA database on PM2.5 emissions in the local region of interest. The method has been illustrated using data from the Pittsburgh Air Quality Study, and suggests that local sources can be very important in affecting PM2.5 exceedances. The results have implications for many of the urban areas in the eastern United States downwind of large sources in the Midwest, and shows that simple statistical tests can be of value in identifying regions where further testing with sophisticated air quality dispersion models and source-receptor models is warranted.

Innovative Assessment of Household Pesticide Exposure Using Linkage to EPA Databases

ISEE-457 Objective: Household pesticide use has been associated with an increased risk of childhood leukemia in case-control studies. These results are based largely on self-reported pesticide use that is limited by potential recall bias and a lack of information on active ingredients. Here we describe a method for objectively characterizing household pesticide exposure by linking EPA registration numbers collected from products stored in the homes to publicly available EPA databases, thus allowing for identification of active ingredients, chemical formulation, intended target pest, and potential toxicity for each product. Material and Methods: Participants enrolled in the Northern California Childhood Leukemia Study (NCCLS), a case-control study, who were less than 8 years of age and residentially stable were eligible for a follow-up interview in which interviewers conducted an inventory of pesticide products stored in the home. Among 367 households enrolled from 2001 to 2005, we obtained detailed information from respondents for 4045 products (mean number per household: 4.89; range: 0–27) including the EPA registration number, storage location, pest treated, method of application, location of use, who applied the product, and the time period and frequency of use. Results: EPA registration numbers were successfully linked to EPA databases for 3006 (74%) products of which 71% were insecticides and 17% herbicides. Pyrethrins (15.4%), glyphosate (6.8%), and permethrins (5.0%) were the most frequent active ingredients contained in the products found in the homes, usually in the form of pressurized liquids (40%) and ready-to-use solutions (24%). Conclusions: The information obtained from the EPA database will allow us to conduct analyses by specific active ingredients and toxicity characteristics of the products and will complement information obtained from self-reports and household dust sampling currently underway in the NCCLS.

Modeling Brominated Trihalomethane Compounds in Drinking Water at a Treatment Plant in Beaumont, Texas

The premise of this study is that the presence of bromide has a substantial effect on both the speciation and total formation of trihalomethane (THM). Consequently, models of water containing substantial bromide concentrations require refinement because they are only calibrated with raw water with high humic acid content. This study investigates and reports efforts on such refinement. The objectives of work reported in this paper are to formulate and validate a new correlative model that is based on physical principles and incorporates high levels of bromide that affect THM formation using raw water rich in both humic and fulvic acid. Two types of THM precursors are considered in the model discussed in this paper: (1) activated aromatic groups, which are more reactive with chlorine than with bromine, and (2) aliphatic groups, which are more reactive with bromine than with chlorine. Aliphatic and aromatic carbons are incorporated in the model by the inclusion of pertinent variables such as C/N and Br/Cl2 in the algorithm. The model also includes NH4 +. This variable affects chlorine consumption that, in turn, potentially affects THM formation. For the first time ever, organic carbon to organic nitrogen and bromide to chlorine ratios is also used as variables potentially affecting THM formation when treating drinking water. The THM model formulated in this paper is an empirical model based on scientific principles and not simply a regression equation. The formulated model is pronounced valid based on a validation effort that employs a portion of an EPA database that was not used for model formulation.