Environmental Protection Agency Guidelines Research Articles

Derivation of a no-significant-risk-level for tetrabromobisphenol A based on a threshold non-mutagenic cancer mode of action.

A no‐significant‐risk‐level of 20 mg day–1 was derived for tetrabromobisphenol A (TBBPA). Uterine tumors (adenomas, adenocarcinomas, and malignant mixed Müllerian) observed in female Wistar Han rats from a National Toxicology Program 2‐year cancer bioassay were identified as the critical effect. Studies suggest that TBBPA is acting through a non‐mutagenic mode of action. Thus, the most appropriate approach to derivation of a cancer risk value based on US Environmental Protection Agency guidelines is a threshold approach, akin to a cancer safe dose (RfDcancer). Using the National Toxicology Program data, we utilized Benchmark dose software to derive a benchmark dose lower limit (BMDL10) as the point of departure (POD) of 103 mg kg–1 day–1. The POD was adjusted to a human equivalent dose of 25.6 mg kg–1 day–1 using allometric scaling. We applied a composite adjustment factor of 100 to the POD to derive an RfDcancer of 0.26 mg kg–1 day–1. Based on a human body weight of 70 kg, the RfDcancer was adjusted to a no‐significant‐risk‐level of 20 mg day–1. This was compared to other available non‐cancer and cancer risk values, and aligns well with our understanding of the underlying biology based on the toxicology data. Overall, the weight of evidence from animal studies indicates that TBBPA has low toxicity and suggests that high doses over long exposure durations are needed to induce uterine tumor formation. Future research needs include a thorough and detailed vetting of the proposed adverse outcome pathway, including further support for key events leading to uterine tumor formation and a quantitative weight of evidence analysis.

The Physico-Chemical Quality of Streams and Channels Draining into River Rwizi, South Western Uganda

There is an increased human population along the catchment area of river Rwizi who are engaged in various activities with potential to contaminate river Rwizi especially along the streams. Studies have been done to examine the physico-chemical quality of the mainstream river Rwizi in Mbarara Municipality. However, the comprehensive source of contamination may be beyond the municipality and yet the streams have not been investigated to substantiate their contribution on quality degradation of the river and this formed the basis of the study. This study determined the physico-chemical parameters of streams draining into river Rwizi. Raw water was purposively selected from streams in the upstream, midstream and downstream sections of the river. Water samples were analyzed for 15 physico-chemical parameters including dissolved oxygen (DO), colour, turbidity, total suspended solid (TSS), total iron (Fe), phosphates (PO3-4), alkalinity, magnesium (Mg), calcium carbonate (CaCO3), temperature, pH, ammonium (NH+4), electrical conductivity (EC), chloride (Cl) and nitrates (NO3). The water samples were analyzed following the standard methods of American Public Health Association and standard operating manual (1985). The obtained values were also compared with the international Environmental Protection Agency (EPA, 2001) guidelines for water quality and the National Environment Management Authority (NEMA, 1999) standards for waste water. The results showed that most of the streams in the downstream generally recorded the highest levels (p i.e. bus park stream (temperature, 27.6°C; colour, 431.17 TCU; TSS, 99.33 mg/l; alkalinity, 468.33 mg/l; Mg, 121.89 mg/l; CaCO3, 588.67 mg/l; Cl, 333.33 mg/l), Kikutu stream (turbidity, 123.58 NTU; EC, 698 μs/cm; DO, 55.73 mg/l; PO3-4, 12.85 mg/l), Kakyeka upper (pH, 10.52; NH+4, 46.67 mg/l), Rwentondo (Fe, 3.44 mg/l) and Kakyeka GBK (NO3, 10.83 mg/l). Most of the parameters downstream were higher than the EPA guideline (temperature, 25°C; colour, 20 - 150 TCUs; TSS, 50 mg/l; alkalinity, 400 mg/l; Cl, 250 mg/l; DO, 5 mg/l; PO3-4, 0.5 - 0.7 mg/l; pH, 5.5 - 9.0; NH+4, 0.2 - 4 mg/l; Fe, 0.2 - 2.0 mg/l) and NEMA standards (colour, 300 TCUs; Mg, 100mg/l; DO, 5mg/l; PO3-4, 10 mg/l; pH, 6.0 - 8.0). On the other hand, the streams in the upstream registered the lowest values of the parameters i.e. Kibimba (temperature, 17.28°C; EC, 31 μs/cm; PO3-4, 0.24 mg/l), Kasharara (colour, 15.17 TCU; TSS, 2.5 mg/l; pH, 6.23; alkalinity, 19.67 mg/l; DO, 9.99 mg/l; Mg, 4.41 mg/l; CaCO3, 23.17 mg/l) and Karungu (turbidity, 7.02 mg/l; Fe, 0.12 mg/l). Calcium carbonate hardness of the waters ranged from soft to excessively hard across the stream. The variations of the parameters detected in the streams in the downstream could reach adverse conditions if no intensive measures are taken to regulate the different anthropogenic activities within the catchment of river Rwizi.

Performance Assessment of the Rehabilitated Mudor Sewage Treatment Plant at James Town Accra-Ghana

The Rehabilitated Mudor sewage treatment plant at James Town was monitored over a period of 4 months (October 2017 to January 2018). This study analyzed the physical, chemical and biological parameters of the raw sewage and the treated effluent from the plant. The result indicates that the total removal efficiencies were 98.8%, 91.2%, 62.8%, 28.6%, 81.7%, 43.6%, 82.5% and 99.6% for BOD, COD, TSS, Nitrate-Nitrogen, Phosphate-Phosphorus, Ammonia-nitrogen, Sulphate and faecal coliform respectively. More than 13 parameters needed to be met according to the Ghana Environmental Protection Agency (EPA) guideline were satisfactorily met whiles ammonia, total suspended solids and phosphate were slightly out of range. From the results obtained, the overall performance of the rehabilitated plant was satisfactory and has seen some improvement with respect to the former recorded performance of the plant. With monitoring operation parameters for waste water plants discharge guidelines becoming stringent over the past years, it could be said that management of the Mudor rehabilitated treatment plant is on the right cause with full scale operation of the plant barely less than a year. Increase in the process steps through rehabilitation resulted in several significant improvements in effluent quality parameters.

Detrimental Effects of Heavy Metals in Soil, Plants, and Aquatic Ecosystems and in Humans.

Environmental pollution has posed a major threat to flora as well as fauna for the past few decades. Industries release effluents into the environment which act as the major source of pollution. The hazardous effects of heavy metals released from these industries impact the soil and due to bioaccumulation of these compounds in the food chain, they ultimately result in a serious human health hazard. The concentration of metals like chromium (Cr), lead (Pb), nickel (Ni), cadmium (Cd), zinc (Zn), titanium (Ti), cobalt (Co), and several others in plants as well as in aquatic animals is above permissible limits according to the World Health Organization (WHO) and the Federal Environmental Protection Agency (FEPA) guidelines. This is why we need to prevent the aquatic ecosystem and human health from detrimental effects. In this review we will be discussing the harmful effects of these metals on soil, plants, aquatic ecosystems, and human health.

Specific colorimetric detection of Fe3+ ions in aqueous solution by squaraine-based chemosensor.

A new squaraine based chemosensor TSQ was developed for colorimetric detection of Fe3+ ions. A thymine moiety in TSQ was constructed to act as an ion acceptor. The sensor displayed an instant colorimetric response specific to Fe3+ over the other metal ions in 20% AcOH–H2O solution. The limit of detection was much lower than that of the environmental protection agency guideline (5.37 μM) in drinking water. A 1 : 1 binding between TSQ and Fe3+ ion was evidenced by Job's plot measurement, ESI-MS and Fourier transform infrared (IR) measurements. Moreover, the proposed sensing mechanism of the receptor towards Fe3+ was strongly supported by DFT calculation. Finally, the sensor has proven to be suitable in real sample applications.

Chemical characterization and quality assessment of some bottled water brands from the Kohgiluyeh-va-Boyer Ahmad province market, SW Iran

Recently, bottled water consumption has been increased in Iran, because of the priority change from tap water to bottled water usage; therefore, conducting studies on quality control of the bottled drinking waters seems very necessary. In this study, a comparison between the amounts of mineral elements present in 10 bottled water brands from the Kohgiluyeh-va-Boyer Ahmad Province market, SW Iran, and recommended limits by national and international standards and guidelines for drinking water was carried out, with the aim to assess the quality of bottled waters as an outdoor supply source for drinking water. The chosen bottled water brands were analyzed for more than 50 physicochemical parameters, using inductively coupled plasma optical emission spectrometry (ICP-OES), ionic chromatography (IC), hydride generation atomic absorption spectroscopy (HGAAS), spectrophotometry, titration, and conductometry standard methods. The comparison between obtained results and Iranian, United States Environmental Protection Agency (USEPA) and World Health Organization (WHO) standards and guidelines showed that all levels of analyzed parameters do not exceed the permitted limits, indicating that the bottled waters have safe quality for drinking use. Results revealed that bottled waters are a valid substitute of tap water, especially for outdoor drinking purpose. Nevertheless, the mineral elements such as Ca, Mg, Na, and K are not provided by the bottled waters in sufficient levels needed daily by human body.

A highly selective colorimetric chemosensor for sequential detection of Fe3+ and pyrophosphate in aqueous solution

A novel colorimetric chemosensor 1 was designed and synthesized for Fe3+/2+ and pyrophosphate (PPi). Sensor 1 showed highly selective and sensitive naked-eye color change to Fe3+ and Fe2+ from yellow to brown in a near-perfect aqueous solution. The detection limits of sensor 1 to Fe3+ and Fe2+ were estimated to be 0.51 μM and 1.15 μM, respectively, which were much lower than the environmental protection agency guideline (5.37 μM) in drinking water. Significantly, sensor 1 could be used for analytical quantification of Fe3+ in real water samples. Moreover, the resulting 1-Fe3+ complex could sense pyrophosphate through naked-eye over various anions especially including phosphate-based anions, showing recovery from 1-Fe3+ to 1 via demetallation. The detection limit of pyrophosphate was determined to be 6.11 μM in aqueous solution. The sensing mechanisms for Fe3+/2+ and PPi were proposed by UV–vis titrations, Job plots, and ESI-mass spectrometry analyses.

Retrospective on The United States Environmental Protection Agency's guidelines for deriving ambient water quality criteria.

Retrospective on The United States Environmental Protection Agency's guidelines for deriving ambient water quality criteria.

Development of biotic ligand model-based freshwater aquatic life criteria for lead following us environmental protection agency guidelines.

The US Environmental Protection Agency's (USEPA's) current ambient water quality criteria (AWQC) for lead (Pb) in freshwater were developed in 1984. The criteria are adjusted for hardness, but more recent studies have demonstrated that other parameters, especially dissolved organic carbon (DOC) and pH, have a much stronger influence on Pb bioavailability. These recent studies have been used to support development of a biotic ligand model (BLM) for Pb in freshwater, such that acute and chronic Pb toxicity can be predicted over a wide range of water chemistry conditions. Following USEPA guidelines for AWQC development and using a methodology consistent with that used by the USEPA in developing its recommended BLM-based criteria for copper in 2007, we propose acute and chronic BLM-based AWQC for Pb in freshwater. In addition to the application of the BLM approach that can better account for site-specific Pb bioavailability, the toxicity data sets presented are much more robust than in 1984, and there are now sufficient chronic Pb toxicity data available that use of an acute-to-chronic ratio is no longer necessary. Over a range of North American surface waters with representative water chemistry conditions, proposed acute BLM-based Pb criteria ranged from approximately 20 to 1000 μg/L and chronic BLM-based Pb criteria ranged from approximately 0.3 to 40 μg/L. The lowest criteria were for water with low DOC (1.2 mg/L), pH (6.7), and hardness (4.3 mg/L as CaCO3), whereas the highest criteria were for water with high DOC (9.8 mg/L), pH (8.2), and hardness (288 mg/L as CaCO3 ). Environ Toxicol Chem 2017;36:2965-2973. © 2017 SETAC.

Physicochemical properties of a flowing stream in Jabi, Abuja, Nigeria

The physicochemical qualities of flowing stream located in Jabi, Abuja, Nigeria was assessed over the duration of 3 months. Parameters measured include pH, temperature, electrical conductivity, turbidity, biological oxygen demand (BOD), dissolved oxygen, chemical oxygen demand, nitrate, sulphate, acidity, alkalinity, and carbon levels and these were simultaneously monitored in the flowing stream using standard methods. Unacceptably, high levels of the assayed parameters were observed in Nitrate (1.39 to 1.44 mg/L), while dissolved oxygen (3.2 to 11.6 mg/L) and turbidity (8.6 to 9.1 NTU) were totally outside the compliance levels of the Federal Environmental Protection Agency (FEPA) Guidelines and World Health Organization (WHO) tolerance limits for domestic uses. The study has revealed that there was an adverse impact on the physiochemical characteristics of the flowing stream as a result of discharge of inadequately treated waste products from surrounding communities. This poses a health risk to several rural communities which rely on flowing stream primarily as their sources of domestic water and also harmful to aquatic life. There is need for the intervention of appropriate regulatory agencies to ensure flowing stream is hygienic for consumption and aquatic life through proper channelling.

A selective distance-based paper analytical device for copper(II) determination using a porphyrin derivative

Meso-tetrakis(1,2-dimethylpyrazolium-4-yl)porphyrin sulfonate (TDMPzP), a water-soluble porphyrin derivative, was synthesized and used as a colorimetric reagent for Cu2+ detection on a microfluidic paper-based analytical device (µPAD) using distance-based quantification. TDMPzP showed a high selectivity for Cu2+ detection in aqueous solutions. When Cu2+ was added to the TDMPzP under acidic conditions, a color change from green to a pink was observed by the naked eye. Under optimized conditions, the application of this system to a distance-based μPAD exhibited good analytical response. The presence of common metal ions (Al3+, Fe3+, Mg2+, Co2+, Mn2+, Zn2+, Pb2+, Cd2+, Sn2+, and Ni2+) did not interfere with Cu2+ detection within reasonable tolerance ratios. The lowest concentration of copper that could be measured was 1mgL−1 (1ppm) which meets the requirements for drinking water contamination regulations from the US Environmental Protection Agency (EPA) and World Health Organization (WHO) guidelines for drinking water. Real drinking water samples were analyzed to confirm the practical application of this system and the results showed good agreement with ICP-MS data. This distance-based µPAD based on TDMPzP for Cu2+ detection is convenient and effective for real-time drinking water analysis.

Quantitative source apportionment and human toxicity of indoor trace metals at university buildings

This study focuses on the source apportionment principal component analysis of indoor particulate matter (PM10) composition in two university buildings with different ventilation systems. A low volume sampler using Teflon filter paper was used to collect the PM10 samples and inductively coupled plasma mass spectrometry was used to determine the concentration of heavy metals. The potential human health damage due to the inhalation of carcinogenic and non-carcinogenic elements was also determined based on the USEPA standard. The results showed PM10 concentrations recorded in Building 1 and Building 2 ranged between 19.1 and 237 μg m−3 and 23.4–159 μg m−3, respectively. In Building 1, the principal component analysis (PCA) and multiple linear regression (MLR) showed that the main sources of pollutants in PM10 were the crustal source (20%), indoor-induced (8%), urban origin (7%) and the Earth's crust (6%). The main sources of pollutants in Building 2 were combustion (21%), biogenic (6%), anthropogenic (4%) and crustal (3%). The effective lifetime carcinogenic risks (ELCR) in Buildings 1 and 2 were 1.90E-3 and 1.65E-4, respectively. The hazard quotient (HQ) represents the non-carcinogenic risk, with 7.73 and 6.46 in Building 1 and Building 2, respectively. These ECLR and HQ values exceed the acceptable limit and are higher compared to the standard from the United States Environmental Protection Agency's Guidelines for the assessment of carcinogen risk. It was suggested that different types of ventilation influence the PM10 distribution in buildings and associated risks towards the occupant's health and indoor air quality.

A novel colorimetric chemosensor for multiple target metal ions Fe2+, Co2+, and Cu2+ in a near-perfect aqueous solution: Experimental and theoretical studies

A selective and multifunctional chemosensor 1 for Fe2+, Co2+ and Cu2+ was designed and synthesized. 1 could simultaneously detect Fe2+, Co2+ and Cu2+ by changing its color from colorless to pink (Fe2+) and to yellow (Co2+ and Cu2+), respectively, in a near-perfect aqueous solution. The binding modes of 1 to Fe2+, Co2+ and Cu2+ were determined to be a 1:1, 2:1, and 1:1, respectively, through Job plot and ESI-mass spectrometry analysis. The detection limits (0.43μM, 0.11μM and 0.28μM) of 1 for Fe2+, Co2+ and Cu2+ were much lower than the US Environmental Protection Agency (EPA) guidelines (5.36μM for Fe2+ and 1.7μM for Co2+) and the WHO guideline (31.5μM for Cu2+) for the drinking water. Moreover, the chemosensor 1 could be used to quantify Fe2+, Co2+ and Cu2+ in water samples, and applied to test kits for detecting Fe2+, Co2+ and Cu2+. The sensing mechanisms of Co2+ and Cu2+ by 1 were supported by theoretical calculations.

Characterization and geochemistry of technogenic magnetic particles (TMPs) in contaminated industrial soils: Assessing health risk via ingestion

The objective of this study was the detailed characterization of “technogenic” magnetic particles (TMPs) separated from contaminated industrial soils. Moreover, non-carcinogenic health risk posed by “technogenic” metals Pb and Zn via the ingestion exposure pathway was carried out. Volume magnetic susceptibility (κ) was measured directly in the field around a chemical industry in Sindos industrial area, Northern Greece. Representative soil samples were collected from the sites where elevated κ values were recorded. Mass specific magnetic susceptibility (χlf) depended on the content of TMPs and ranged from 52.6×10−8m3kg−1 to 821.2×10−8m3kg−1 with the maximum values detected in the immediate vicinity of the industrial unit where the most contaminated soils were also identified. Mineralogically the TMPs exhibited a dominant iron spinel phase, while other iron-bearing phases such as hematite and lepidocrocite were detected. Morphologically, Fe-rich spherules and irregular-shaped particles were the most commonly observed particles in TMPs, revealing various Fe contents often associated with elevated heavy metal contents. TMPs exhibited significantly higher concentrations of trace elements compared to non-magnetic fractions (NMFs) indicating that potentially harmful elements (PHEs) are preferentially enriched in the TMPs. Furthermore, for the first time, a health risk assessment study for the incidental soil magnetic fractions (MFs) ingestion of the “technogenic” metals Pb and Zn was carried out based on U.S. Environmental Protection Agency (U.S.E.P.A.) guidelines, incorporating oral bioaccessibility measurements using the BARGE Unified Bioaccessibility Method (UBM). Significant fractions (>50%) of Pb and Zn occur in bioaccessible forms in the TMPs and both children and adults are experiencing potential health risk since determined HQs values were significantly higher than safe level (=1).

Impacts of iron and steelmaking facilities on soil quality

Iron and steel are highly important materials used in a wide range of products with important contribution to the economic development. The processes for making iron and steel are energy intensive and known to contribute to local pollution. Deposition of the metals may also have adverse impacts on soil quality, which requires detailed assessment. The aim of this study was to investigate the impacts of iron and steelmaking facilities on the local soil quality. Soil samples were collected in the vicinity of two steelmaking sites in Australia, one based on blast furnace steelmaking operation, while the second site was based on electric arc furnace steel recycling. The soil samples were compared to a background site where no industrial impact is expected. The soil collected near industrial facilities contained larger toxic metal contents, however this concentration for all priority metals was within the Australian National Environmental Protection Measure guidelines for the acceptable recreational soil quality. When compared to the international soil quality guidelines, some of the soils collected near the industrial sites, particularly near the blast furnace operated steelmaking, exceeded the arsenic, iron and manganese (according to United States Environmental Protection Agency guidelines) and chromium, copper and nickel concentrations (according to the Canadian guidelines). The work further provided a novel environmental assessment model taking into consideration the environmental and health impacts of each element. The environmental assessment revealed most significant contribution of manganese, followed by titanium, zinc, chromium and lead. Titanium was the second most important contributor to the soil quality, however this metal is currently not included in any of the international soil quality guidelines.

Characteristics, Sources, and Health Risks of Atmospheric PM2.5-Bound Polycyclic Aromatic Hydrocarbons in Hsinchu, Taiwan

ABSTRACTThis study investigated PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) in order to determine the seasonal changes in total benzo[a]pyrene equivalent (BaPeq) concentrations and to identify contamination sources by using a positive matrix factorization model, a conditional probability function, and characteristic ratios of PAHs in Hsinchu. The sampling period was from September 2014 to August 2015. PM2.5 samplers equipped with 47-mm quartz membrane filters were operated at a flow rate of 16.7 L min–1 for 48 h. The concentrations of 20 PAHs were determined through gas chromatography–mass spectrometry. The results revealed the PM2.5, total PAHs, and BaPeq mass concentrations in the four seasons ranged from 4.91 to 58.5 µg m–3, 0.21 to 8.08 ng m–3, and 0.03 to 0.78 ng m–3, respectively. The PM2.5, total PAHs, and BaPeq mass concentrations were in the order winter > autumn > spring > summer and exhibited significant seasonal variations. The carcinogenic potency of PAHs in winter was approximately 6.21 times higher than that in summer. The major BaPeq contributors were BaP, BbF, INP, and DBA. BaP accounted for 49.0% of BaPeq concentrations in PM2.5 in all four seasons. The annual average lifetime excess cancer risk of PM2.5-bound PAHs (1.60 × 10–5) was higher than that specified in the United States Environmental Protection Agency guidelines (10–6). The two major sources were stationary emission sources and unburned petroleum and traffic emissions, which together accounted for 90.3% of PM2.5-bound PAHs.

Risk assessment of haloacetic acids in the water supply of Tehran, Iran

Disinfection by-products are compounds occurring in drinking water as a result of reactions between disinfectants and impurities in raw water, and their occurrence has been a public health concern for the last four decades. Haloacetic acids (HAAs) are one of the major by-products of chlorination. The concentration and variation of HAAs was monitored in 540 samples taken from tap water in six water and wastewater districts of Tehran, Iran. Seasonal variation indicated that natural organic matter and HAA levels were much higher in the spring and fall seasons. The concentrations of HAAs in drinking water samples varied with water sources. They were higher in drinking water obtained from surface water. In this study, the analysis method of human health risk assessment with regard to exposure to HAAs by drinking water in Tehran was based on the United States Environmental Protection Agency (USEPA) guideline. It was found from these studies that the risk to human health appears to be negligible.

Colorimetric detection of Fe3+ and Fe2+ and sequential fluorescent detection of Al3+ and pyrophosphate by an imidazole-based chemosensor in a near-perfect aqueous solution

A novel chemosensor was designed and synthesized for various analytes: Fe3+, Fe2+, Al3+ and pyrophosphate. The sensor showed a selective color change from yellow to orange toward both Fe3+ and Fe2+ in a near-perfect aqueous solution, which could be reusable simply through treatment with ethylenediaminetetraacetic acid. The detection limits (0.27 μM and 0.32 μM) for Fe3+ and Fe2+ were much lower than the environmental protection agency guideline (5.37 μM) in drinking water. The sensor could be used to quantify Fe3+ in real water samples. Moreover, this sensor acted as a ‘turn-on’ and ‘turn-off’ type fluorescent sensor toward Al3+ and pyrophosphate. The sensing mechanism of the sensor for Al3+ could be explained by chelation-enhanced fluorescence effect, which was supported by theoretical calculations. Through a metal-complex displacement method, the sensor-Al3+ complex selectively responded to pyrophosphate over various anions especially including phosphate-based anions. Interestingly, the sensor could be used to sequentially detect both Al3+ and pyrophosphate in the living cells.

Legacy lead arsenate soil contamination at childcare centers in the Yakima Valley, Central Washington, USA

BackgroundFrom the early 1900s to the 1950s, Yakima Valley orchards were commonly treated with lead arsenate (LA) insecticides. Lead (Pb) and arsenic (As) soil contamination has been identified on former orchard lands throughout Central Washington and pose a threat to human health and the environment. ObjectivesThe levels of Pb and As in soil and interior dust at participating childcare centers in the Upper Yakima Valley (Yakima County), Washington were sampled to explore exposure potential for young children. MethodsChildcare center soils were collected from two soil depths, homogenized, and analyzed in bulk by a field-portable X-ray fluorescence spectrometer (XRF). Interior dust wipes samples were collected from at least two locations in each facility. All soil samples >250 mg/kg Pb and/or >20 As mg/kg were sieved to 250 μm, tested by XRF a second time, and analyzed via acid digestion and inductively coupled plasma mass spectrometry (ICP-MS) analysis. ResultsBulk and sieved XRF results, as well as ICP-MS to XRF results were strongly correlated. Maximum Pb and As XRF results indicated that 4 (21%) and 8 (42%) of the 19 childcare centers surveyed exceeded the regulatory standard for Pb and As, respectively. Historic land use was significantly associated with elevated Pb and As levels. Interior dust loadings were below United States Environmental Protection Agency (EPA) guidelines. ConclusionsChildcare centers are areas of intensive use for children and when coupled with potential residential exposure in their homes, the total daily exposure is a potential hazard to children.

A novel colorimetric chemosensor for detection of Co2+ and S2− in an aqueous environment

A novel multifunctional and highly selective chemosensor 1, N 2-(bis(pyridin-2-ylmethyl)amino)-N-(2-((2,4-dinitrophenyl)amino)phenyl)acetamide, for Co2+ and S2− was designed and synthesized. Sensor 1 showed a selective colorimetric sensing ability for cobalt ion by changing color from pale yellow to light green in a near perfect aqueous solution. The detection limit (0.99μM) of 1 for Co2+ was lower than the Environmental Protection Agency (EPA) guideline (1.7μM) for drinking water. The sensor 1 could be used to quantify Co2+ in water samples. Moreover, sensor 1 detected S2− selectively, which induced an obvious color change from pale yellow to pink over most other competitive anions in aqueous solution. The sensing mechanism of Co2+ by 1 was proposed to be a ligand-to-metal charge-transfer (LMCT) with the experimental results and theoretical calculations, and that of S2− by 1 proposed to be a deprotonation process. Therefore, this sensor 1 could be used as a practical system for monitoring both Co2+ and S2− in an aqueous environment.