Evaluation of the potentials of rice varieties and water management practices for reducing human health risks associated with polluted river water irrigated rice in Bangladesh.

The consumption of arsenic and trace-metal-contaminated rice is a human health concern worldwide, particularly in Bangladesh. In this study, the effects of rice varieties and water management practices on the concentrations of arsenic and trace metals in rice grains were investigated to reduce human health risks related to rice consumption. In addition, the performance of risk reduction using the optimum combination of rice variety and water management practices was quantitatively assessed using Monte Carlo simulation, in which non-carcinogenic and carcinogenic risk distributions under the status quo and the optimum combination were compared. The experimental results revealed that Dular and BRRI dhan45 (rice varieties) cultivated under alternate wetting and drying (AWD) and continuous flooding (CF) conditions showed the lowest hazard quotient (HQ) values for copper, cadmium, and arsenic and the lowest target cancer risk (TR) for arsenic. In Dular and BRRI dhan45 (AWD and CF) varieties, the proportion of the population for which HQs exceeded 1.0 (the reference value) tended to decrease (except for arsenic), compared with populations for which the rice varieties and water management practices were not specified. These results suggest that the use of optimum combinations of rice varieties and water management practices could reduce non-carcinogenic and carcinogenic risks associated with arsenic and trace metals uptake via rice grain consumption by the Bangladeshi people.

Antibiotics, antibiotic-resistant bacteria, and resistance genes in aquaculture: risks, current concern, and future thinking.

Aquaculture is remarkably one of the most promising industries among the food-producing industries in the world. Aquaculture production as well as fish consumption per capita have been dramatically increasing over the past two decades. Shifting of culture method from semi-intensive to intensive technique and applying of antibiotics to control the disease outbreak are the major factors for the increasing trend of aquaculture production. Antibiotics are usually present at subtherapeutic levels in the aquaculture environment, which increases the selective pressure to the resistant bacteria and stimulates resistant gene transfer in the aquatic environment. It is now widely documented that antibiotic resistance genes and resistant bacteria are transported from the aquatic environment to the terrestrial environment and may pose adverse effects on human and animal health. However, data related to antibiotic usage and bacterial resistance in aquaculture is very limited or even absent in major aquaculture-producing countries. In particular, residual levels of antibiotics in fish and shellfish are not well documented. Recently, some of the countries have already decided the maximum residue levels (MRLs) of antibiotics in fish muscle or skin; however, many antibiotics are yet not to be decided. Therefore, an urgent universal effort needs to be taken to monitor antibiotic concentration and resistant bacteria particularly multiple antibiotic-resistant bacteria and to assess the associated risks in aquaculture. Finally, we suggest to take an initiative to make a uniform antibiotic registration process, to establish the MRLs for fish/shrimp and to ensure the use of only aquaculture antibiotics in fish and shellfish farming globally.

Vertical profiles of legacy organochlorine pesticides in sediment cores from lake Nakaumi, Japan.

Two sediment core samples from the brackish Lake Nakaumi in Japan were analyzed to determine the historical profiles of organochlorine pesticides (OCPs). It was observed that from the 1940s to 2005, the vertical distribution of OCPs in sediment cores reflected the temporal trend of pesticide usage in Japan. Dichlorodiphenyltrichloroethane (DDT) and its metabolites were predominant, with concentrations of 0.008-8.27 ng g-1 dry weight, and their contribution to ΣOCPs was over 58%. The results also confirmed that the DDTs in the sediment cores originated from past input. Further, even though hexachlorocyclohexanes were the most used OCP in Japan, their residual concentrations were lower than those of DDTs and chlordane related compounds (CHLs). The concentrations of CHLs were 0.163-1.539 ng g-1 dry weight, whereas hexachlorobenzene (HCB), drins, heptachlor, and mirex showed very low concentrations. Interestingly, although HCB was never registered as a pesticide in Japan, it was detected in both core samples. This HCB contamination might be attributed to pentachlorophenol. Additionally, the hierarchical cluster analysis results corresponding to both sediment cores could be classified under four groups based on a similarity of over 50%. The results also showed that the OCP burden in Lake Nakaumi for the past 60 years was 130 kg and 1153 kg at Honjo and at the center of Lake Nakaumi, respectively. Overall, the results of this study indicate that the distribution of OCPs in Lake Nakaumi reflects the trend of pesticide usage in Japan.

Chronic toxicity of 50 metals to Ceriodaphnia dubia.

Metals are essential elements for human life but may cause disorders when exposure is excessive. Previously, we reported on the acute toxicity of 50 metals; however, the chronic toxicity data of some metals are not available. Therefore, we conducted chronic toxicity tests to determine the effects of 50 metals on the water flea, Ceriodaphnia dubia. The IC20 of 20 metals (Be, Sc, Cr, Co, Ni, Cu, Zn, Y, Ru, Ag, Cd, In, Te, W, Os, Pt, Au, Hg, Tl and Pb) were <100 µg/L; nine metals (Al, V, As, Se, Zr, Nb, Rh, Sb and Bi) were 100 ≤ IC20 < 1000 µg/L; 16 metals (Li, Mg, K, Ti, Mn, Fe, Ga, Ge, Rb, Sr, Mo, Sn, Cs, Ba, Re and Ir) were 1000 ≤ IC20 ≤ 100 000 µg/L; and two metals (Na and Ca) were >100 000 µg/L. Three metals (Pd, Hf and Ta) did not show IC20 at the upper limit of respective aqueous solubility, and IC20 s were not obtained. The maximum test concentrations (almost aqueous solubility) of Pd, Hf and Ta were 83, 2400 and 5.3 µg/L, respectively. These data show the high correlation between our IC50 s for C. dubia and those for Dahpnia magna published previously. The IC50 s of 47 metals were not correlated with electronegativity, first ionization energy, atomic weight, atomic number, covalent radius, atomic radius or ionic radius.

Does a sum of toxic units exceeding 1 imply adverse impacts on macroinvertebrate assemblages? A field study in a northern Japanese river receiving treated mine discharge.

In ecological risk assessment, sum-of-toxic-unit approaches based on measured water quality factors such as trace metals are used to infer ecological impacts in the environment. However, it is uncertain whether the use of such approaches yields accurate risk predictions. To address this issue, we investigated and compared (1) water quality, including trace metals, and (2) benthic macroinvertebrate communities in a northern Japanese river receiving treated discharge from an abandoned mine and in a nearby reference river. As a sum-of-toxic-unit approach, we employed a cumulative criterion unit (CCU), namely, the sum of the ratios of the dissolved concentrations of a metal (Cu, Zn, Cd, or Pb) divided by the US Environmental Protection Agency hardness-adjusted environmental water quality criterion for that metal. Compared with the reference sites, at the metal-contaminated sites, the richness, abundance, and structure of macroinvertebrate communities were little affected, with CCUs of 1.7 to 7.4, suggesting that CCU values exceeding 1 do not always indicate marked adverse impacts on these metrics. Further study is still required to derive a more compelling conclusion on the generally applicable relationships between CCUs and ecological impacts on river invertebrates. This would lead to better ecological risk assessments based on sum-of-toxic-unit approaches.

Distribution of polycyclic aromatic hydrocarbons (PAHs) in commonly consumed seafood from coastal areas of Bangladesh and associated human health implications.

Levels, distribution, possible sources and potential risks of 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) were investigated comprehensively in frequently consumed seafood species collected from the coastal areas of Bangladesh. Samples were collected in winter and summer, 2015. The total concentration of PAHs (∑PAHs) in the examined seafood was 184.5-2806.6 ng/g wet weight (ww) in winter and 117.9-4216.8 ng/g ww in summer, respectively. The levels of ∑PAHs were comparable to or higher than those reported from other coastal areas. Seasonal variation was not significant for the majority of the monitored PAHs. Spatial distribution revealed that the seafood collected from areas with recent urbanization and industrialization (Chittagong, Cox's Bazar and Sundarbans) was more contaminated with PAHs than those from the unindustrialized area (Meghna Estuary). Low-molecular-weight isomers dominated the PAH composition. Molecular ratios suggested the abundance of mixed sources of PAHs in the Bangladeshi coastal areas with a slight imposition toward the petrogenic origin. A preliminary evaluation of human health risk indicated that the dietary PAH exposure from consumption of Bangladeshi seafood would certainly induce adverse health effects. This finding suggests the need to enhance risk management regarding seafood consumption through public advisory in Bangladesh.

Distribution, Source Apportionment, and Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) in the Surficial Sediments from the Coastal Areas of Bangladesh.

The surficial sediments were collected in winter and summer (2015) from the coastal areas of Bangladesh and analyzed for 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs). The total concentration of PAHs (∑PAHs) were 349.8-11,058.8 and 199.9-17,089.1 ng/g dry weight (dw) in winter and summer, respectively. Sediements from the areas with recent urbanization and industrialization (Chittagong, Cox's Bazar, and Sundarbans) were more contaminated with PAHs than the unindustrialized area (Meghna Estuary). The concentrations of ∑PAHs were slightly higher in summer than those in winter, but the seasonal variations were not statistically significant (p > 0.05). Molecular ratios suggested mixed sources of PAHs in the Bangladeshi coastal areas with a slight imposition of pyrolytic inputs closely related to shipping and fishing activities as well as industrial and municipal sewage discharge. According to ecological risk assessment, the measured levels of sedimentary PAHs exceeded some of the existing national and international environmental quality guidelines/standards, and thus might cause acute biological damage in the studied areas of the Bay of Bengal coast of Bangladesh.

Polychlorinated biphenyls (PCBs) in commonly consumed seafood from the coastal area of Bangladesh: occurrence, distribution, and human health implications.

Dietary intake is the most important route of polychlorinated biphenyls (PCBs) exposure and seafood is the major dietary component for the coastal populations. It is, therefore, an urgent need to assess the levels of PCBs in seafood. A comprehensive congener-specific evaluation of PCBs was carried out for the first time in Bangladesh. All 209 congeners of PCBs in 48 seafood samples (5 finfish and 2 shellfish species) collected in winter and summer of 2015 were measured by GC-MS/MS. Regardless of season and site, the ∑PCBs (ng/g wet weight) in finfish and shellfish were in the range of 6.4-86.2 and 3.8-37.7, respectively. The results were comparable to or higher than those observed in other studies worldwide, particularly from Spain, China, Korea, Thailand, and Hong Kong. No significant seasonal variation was observed in the levels of ∑PCBs in the examined seafood (p > 0.05); however, interspecies differences were significant (p < 0.05). Nonetheless, spatial distribution revealed seafood collected from the areas with recent urbanization and industrialization (Chittagong, Cox's Bazar, and Sundarbans) were more contaminated with PCBs than the area unaffected by industries (Meghna Estuary). Moderately chlorinated (4-6 Cl) homologs dominated the PCB profiles. The congener profile and homolog composition revealed that the source origin of PCBs in the Bangladeshi seafood was related to mixtures of technical PCBs formulations. The dietary exposure assessment revealed that the coastal residents are sufficiently exposed to the dietary PCBs through seafood consumption which may cause severe health risk including dioxin-like toxic effects.

Occurrence, distribution and possible sources of polychlorinated biphenyls (PCBs) in the surface water from the Bay of Bengal coast of Bangladesh.

Full profile of polychlorinated biphenyls (PCBs) in the coastal surface water from Bangladesh were analyzed by GC-MS/MS to explore the status of contamination, spatiotemporal distribution and to trace their potential sources. The total concentrations of dissolved PCBs (∑PCBs, sum of all congeners) varied from 32.17 to 160.7 ng/L and 46.45-199.4 ng/L in winter and summer, respectively, and the ranges were comparable to or higher than those recorded in the surface water from the coastal areas of India, China, Japan, Italy, Belgium and USA. The difference in the levels of PCBs between the two seasons was not statistically significant (p > 0.05). However, spatial distribution revealed that the areas with recent urbanization and industrialization (Chittagong, Cox's Bazar and Sundarbans) were more contaminated with PCBs than the unindustrialized area (Meghna Estuary). Lightly to moderately chlorinated (2-6 Cl) homologs dominated the PCB profiles. Our analyses (congener profile and homolog composition) elucidated that the past and on-going use of PCB-containing equipment (e.g. capacitors and transformers) as well as the anthropogenic activities such as urban developments, commercial and industrial establishments (e.g. ship breaking and port activities) might be the potential sources of PCB emission in Bangladesh. A set of congeners based on their detection frequencies and abundance were identified and categorized as potential environmental marker PCBs, which can be used for the future selective monitoring studies regarding reasonable limitations on full congener assessment. According to the existing national and international water quality guidelines/standards, PCB concentrations recorded in this study could potentially cause biological damage. Essentially, the findings of this first comprehensive report on the PCB contamination in the surface water in Bangladesh may provide a reference to future studies of these compounds in the Bay of Bengal.

Occurrence and ecological risk of pharmaceuticals in river surface water of Bangladesh.

Pharmaceutical contamination in the aquatic environment is a global issue that affects aquatic animals, micro-organisms and human health. The occurrence and preliminary ecological risk of 12 (11 antibiotics and 1 antiepileptic drug) pharmaceuticals were investigated for the first time in the surface water of the old Brahmaputra River, where open-water-fed aquaculture activities are being practiced in Bangladesh. The pharmaceuticals were quantified by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS), operated with positive electrospray ionization (ESI+) and a multiple reaction monitoring (MRM) mode. Nine pharmaceuticals were detected in the river surface water, whereas three were below the limit of detection (LOD). Metronidazole was detected in all the samples with concentrations ranging from 0.05 to 13.51 ng L-1. Trimethoprim had the second highest frequency of detection (95%) with the highest concentration (17.20 ng L-1). The ranges of concentration and detection frequency of sulfonamides and macrolides were

Source characterization and risk of exposure to atmospheric polychlorinated biphenyls (PCBs) in Ghana.

With recent evidence that persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) are emerging in environmental media in some developing countries that otherwise have sparing production and usage history, it has become important to identify such contemporary source factors of PCBs and the risks this may pose, in line with the global consensus on POP management and elimination. The present study investigated contaminations from atmospheric PCBs in Ghana, deciphered source factors, and accessed risk of exposure to dioxin-like PCBs (DL-PCBs). Atmospheric PCBs were monitored by deployment of PUF-disk passive air samplers (PAS) at several sites across Ghana for 56 days. Atmospheric ∑190PCB concentration in Ghana ranged from 0.28 ng/m3 in Kumasi to 4.64 ng/m3 at Agbogbloshie, a suburb in Accra noted for informal electronic waste (e-waste) recycling activities. As high as 11.10 ng/m3 of PCB concentration was measured in plumes from uncontrolled open burning of e-wastes at Agbogbloshie. Applying statistical source characterization tools, it emerged that e-wastes were a major contributor to the environmental burden of atmospheric PCBs in Ghana. The risk of DL-PCB toxicity via inhalation in the Agbogbloshie area was 4.2 pg TEQ/day, within similar order of magnitude of an estimated risk of 3.85 pg TEQ/day faced by e-waste workers working averagely for 8 h per day. It is suggested that elimination of e-waste sites would help to significantly reduce PCB-related toxicity issues in Ghana. Graphical abstract ᅟ.

Atmospheric monitoring of organochlorine pesticides across some West African countries.

Most African countries have ratified the Stockholm Convention on persistent organic pollutants (POPs) and are expected to reduce emissions of POPs such as organochlorine pesticides (OCPs) to the atmosphere. Emerging evidence, however, suggests that there are contemporary sources of OCPs in African countries despite the global ban on these products. This study investigated the atmospheric contamination from OCPs in four West African countries-Togo, Benin, Nigeria, and Cameroon-to ascertain the emission levels of OCPs and the characteristic signatures of contamination. Polyurethane foam (PUF) disk passive air samplers (PAS) were deployed in each country for ca. 55 days in 2012 and analyzed for 25 OCPs. Hexachlorocyclohexanes (HCHs) and DDTs constituted the highest burden of atmospheric OCPs in the target countries, at average concentrations of 441 pg m-3 (range 23-2718) and 403 pg m-3 (range 91-1880), respectively. Mirex had the lowest concentration, ranged between 0.1 and 3.3 pg m-3. The concentration of OCPs in rainy season was higher than in dry season in Cameroon, and presupposed inputs from agriculture during the rainy season. The concentrations of ∑25 OCPs in each country were in the following order: Cameroon > Nigeria > Benin > Togo. There was significant evidence, based on chemical signatures of the contamination that DDT, aldrin, chlordane, and endosulfan were recently applied at certain sites in the respective countries.

Occurrence, distribution, ecological and resistance risks of antibiotics in surface water of finfish and shellfish aquaculture in Bangladesh.

The present study for the first time reports the occurrence, distribution, ecological and resistance risks of antibiotics in the surface water of freshwater finfish and brackish water shellfish aquaculture in Bangladesh. Among the nine targets, seven antibiotics were detected in finfish aquaculture, whereas four in shellfish aquaculture. The concentrations (ranges) and overall detection frequency of sulfamethoxazole (SMX) (nd-20.02 ng L-1 and 73%), trimethoprim (TMP) (nd-41.67 ng L-1 and 60%), tylosin (TYL) (nd-39.34 ng L-1 and 60%), sulfadiazine (SDZ) (nd-17.97 ng L-1 and 53%), sulfamethazine (SMT) (nd-11.71 ng L-1 and 33%), sulfamethizole (SMZ) (nd-10.81 ng L-1 and 40%) and penicillin G (PC_G) (nd-7.83 ng L-1, 7%) were found in finfish aquaculture. In case of shellfish aquaculture, the concentrations (ranges) and overall detection frequency were for SMX (nd-16.77 ng L-1 and 67%), TMP (nd-11.39 ng L-1 and 20%), TYL (nd-0.16 ng L-1 and 20%) and erythromycin-H2O (ERY-H2O) (nd-3.91 ng L-1 and 20%). The present findings revealed that finfish aquaculture is more contaminated with the higher numbers and concentrations of antibiotics. The preliminary ecological and resistance risks assessment showed that the calculated risk quotients (RQs) were lower than one (RQs<1) for all the detected antibiotics in both aquaculture. Preliminary ecological and resistance risks assessment revealed that there were no adverse ecological and resistance risks, however, our study suggests that it is imperative to pay due attention to monitor the antibiotics contamination in rapid growing aquaculture sector of Bangladesh for the reduction of potential risks of antibiotics on aquatic organisms as well as human health.

Chemical speciation of trace metals in the industrial sludge of Dhaka City, Bangladesh.

The objective of this study was to assess total concentration and chemical fractionation of trace metals in the industrial wastewater and sludge collected from seven different types of industries in Dhaka City, Bangladesh. The sludge from industries is either dumped on landfills or reused as secondary resources in order to preserve natural resources. Metals were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). The ranges of Cr, Ni, Cu, As, Cd, and Pb in the sludges were 1.4-9,470, 4.8-994, 12.8-444, 2.2-224, 1.9-46.0 and 1.3-87.0 mg/kg, respectively. As a whole, the average concentrations of trace metals in samples were in the decreasing order of Cr > Ni > Cu > As > Pb > Cd. The results of the Community Bureau of Reference (BCR) sequential extraction showed that the studied metals were predominantly associated with the residual fraction followed by the oxidizable fraction. The study revealed that the mobile fractions of trace metals are poorly predictable from the total content, and bioavailability of all fractions of elements tends to decrease.

Occurrence and assessment of perfluoroalkyl acids (PFAAs) in commonly consumed seafood from the coastal area of Bangladesh.

This study reports the first evidence of the occurrence of PFAAs in commonly consumed seafood from the coastal area of Bangladesh. Fifteen target PFAAs in 48 seafood samples (5 finfish and 2 shellfish species) were measured by HPLC-MS/MS. The ΣPFAAs in finfish and shellfish were in the range of 0.32-14.58 and 1.31-8.34 (ng/g wet weight), respectively. Perfluorooctanesulfonate (PFOS) in finfish (0.1-3.86ng/g ww), whereas perfluorooctanoic acid (PFOA) in shellfish (0.07-2.39ng/g ww) were the most abundant PFAAs. The results were comparable with other studies worldwide, particularly from China, Spain, Sweden, and USA. The majority of monitored PFAAs did not show clear seasonal variation. However, seafood from the southeast area (Cox's Bazar and Chittagong) showed relatively higher levels of PFAAs. Moreover, the dietary exposure assessment revealed that the daily intakes of PFAAs via seafood consumption were far less than the health-based guidelines, indicating low health risk for the Bangladeshi coastal residents.

Organophosphate flame retardants in the indoor air and dust in cars in Japan.

The concentrations of organophosphate flame retardants (OPFRs) in the indoor air and dust were measured in 25 unoccupied cars in Japan. In the indoor air of the cars, most OPFRs were neither detected nor found at a concentration lower than the method quantification limit. The highest concentration (1500 ng m-3) was obtained for tris(1-chloro-2-propyl) phosphate (TCIPP). By contrast, many OPFRs were detected in the dust samples collected from the interior of the cars. TCIPP and tris(2-ethylhexyl) phosphate (TEHP) were present at the highest concentrations at 390 µg g-1 (in dust from car seats) and 640 µg g-1 (in dust from car floor mats), respectively. The highest median concentrations (35 µg g-1 for car seats, 53 µg g-1 for car floor mats) were obtained for tris(2-butoxyethyl) phosphate (TBOEP). According to the results of our exposure assessment, the typical exposures to OPFRs via inhalation in car cabins ranged from 9.0×10-4 to 7.8×10-1 ng kg-bw-1 day-1. The typical exposures to OPFRs via dust ingestion ranged from 9.2×10-4 to 8.8×10-1 ng kg-bw-1 day-1. We compared these results with the ref-erence doses for OPFRs and found that, based on cur-rent information about the toxicities of OPFRs, exposure to OPFRs in car cabins via inhalation and dust ingestion is unlikely to have adverse human health effects.

Revaluation of stockpile amount of PFOS-containing aqueous film-forming foam in Japan: gaps and pitfalls in the stockpile survey.

Stockpiles of perfluoro-octane sulfonic acid (PFOS) containing aqueous film-forming foam (AFFF) have the potential to be emitted by leaching, spills, and during use in fire response and other processes. Several studies have discussed the high levels of stockpiled PFOS-containing AFFF and the risk they pose to the environment; however, there are large gaps in the amounts in Japan compared with other countries. For example, 300 tons are stockpiled in Canada, 2200-2600 tons in Switzerland, 1400 tons in Norway, and 19,000 tons in Japan from their reports for publication. The gap is considered to be a result of lack of surveys of several important sources. In this study, we revaluated the stockpile of AFFF in Japan to verify the reported value and identify the source of this gap based on information available in peer-reviewed papers, governmental reports, and business reports. The major reason for the gap between Japan and other countries was considered to be the survey of stockpiles in car-parking facilities, which accounted for 46.7% of the total amounts in Japan, but were not considered in other countries. These stockpiles indicate a high potential for accidental leaching or spilling of the AFFF by careless storage. Therefore, it is recommended that continual surveys of the AFFF stockpile in car-parking facilities be conducted in the rest of the world.

Acute toxicity reduction and toxicity identification in pigment-contaminated wastewater during anaerobic-anoxic-oxic (A/A/O) treatment process.

In China, a considerable part of industrial wastewater effluents are discharged into the municipal wastewater treatment plants (WWTPs) after pretreatment in their own wastewater treatment plants. Even though the industrial effluents meet the professional emission standards, many micro-pollutants still remained, and they could be resistant in the municipal WWTPs with conventional activated sludge process. Pigment wastewater was chosen in this study, and the acute toxicity reduction and identification of the pigment-contaminated wastewater treated by the conventional anaerobic-anoxic-oxic (A/A/O) process were evaluated. Results indicated that the raw pigment-contaminated wastewater was acutely toxic to Photobacterium phosphoreum (P. phosphoreum), Daphnia magna (D. magna) and Danio rerio (D. rerio). The acute toxicity was decreased in some degree after A/A/O treatment, but the final effluent still exhibited acute toxicity to D. magna and D. rerio with the toxic units (TU) of 1.1 and 2.0, respectively. Chemical analyses showed the presence of various refractory and toxic nitrogen-containing polycyclic and heterocyclic compounds in the pigment-contaminated wastewater. Toxicity identification by combining chemical analyses and correlation analysis showed that N-containing refractory organic toxicants were the main toxicity source for the pigment-contaminated wastewater, and several toxicants showed significant correlation with P. phosphoreum and D. magna. This study indicated that the A/A/O process was not efficient for pigment-contaminated wastewater treatment, and it was irradiative for technology improvement in the WWTPs receiving pretreated industrial wastewater effluents.

Perfluoroalkyl acids (PFAAs) in the Pra and Kakum River basins and associated tap water in Ghana.

Perfluoroalkyl acids (PFAAs) are persistent environmental pollutants that have been detected in various media including human serum. Due to concerns regarding their bioaccumulation and possible negative health effects, an understanding of routes of human exposure is necessary. PFAAs are recalcitrant in many water treatment processes, making drinking water a potential source of human exposure. This study presents the first report on contamination from PFAAs in river and drinking water in Ghana. The targeted PFAAs were perfluoroalkyl carboxylic acids (PFCAs) with C4-14 carbon chain and perfluoroalkane sulphonic acids (PFSAs) with C6, 8, 10. Five PFAA congeners - PFOA, PFOS, PFHxA, PFDA and PFPeA - were commonly detected in river and tap water. The mean concentrations of ∑PFAAs in the Kakum and Pra Rivers were 281 and 398ng/L, while tap water (supplied from the treatment of water from those rivers) contained concentrations of 197 and 200ng/L, respectively. PFOA and PFOS constituted about 99% of the ∑PFAAs. The risk quotient (RQ) attributed to drinking of tap water was estimated at 1.01 and 1.74 for PFOA and PFOS, respectively. For a country that has not produced these compounds, the RQs were unexpectedly high, raising concerns particularly about contamination from such emerging pollutants in local water sources. The study revealed limitations of local tap water treatment in getting rid of these emerging pollutants.

Assessing bioavailability levels of metals in effluent-affected rivers: effect of Fe(III) and chelating agents on the distribution of metal speciation.

To assess the effects of Fe(III) and anthropogenic ligands on the bioavailability of Ni, Cu, Zn, and Pb, concentrations of bioavailable metals were measured by the DGT (diffusive gradients in thin films) method in some urban rivers, and were compared with concentrations calculated by a chemical equilibrium model (WHAM 7.0). Assuming that dissolved Fe(III) (<0.45 µm membrane filtered) was in equilibrium with colloidal iron oxide, the WHAM 7.0 model estimated that bioavailable concentrations of Ni, Cu, and Zn were slightly higher than the corresponding values estimated assuming that dissolved Fe(III) was absent. In contrast, lower levels of free Pb were predicted by the WHAM 7.0 model when dissolved Fe(III) was included. Estimates showed that most of the dissolved Pb was present as colloidal iron-Pb complex. Ethylene-diamine-tetra-acetic acid (EDTA) concentrations at sampling sites were predicted from the relationship between EDTA and the calculated bioavailable concentration of Zn. When both colloidal iron and predicted EDTA concentrations were included in the WHAM 7.0 calculations, dissolved metals showed a strong tendency to form EDTA complexes, in the order Ni > Cu > Zn > Pb. With the inclusion of EDTA, bioavailable concentrations of Ni, Cu, and Zn predicted by WHAM 7.0 were different from those predicted considering only humic substances and colloidal iron.