Ecological risks of heavy metals/metalloid discharged from two sewage treatment works to Mai Po Ramsar site, South China.

The concentrations of six heavy metal/metalloids (HMs) cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb), zinc (Zn), and arsenic (As) were determined in the influent, effluent, and dewatered sludge of two sewage treatment works (Yuen Long Sewage Treatment Work (YLSTW) and Shek Wu Hui Sewage Treatment Work (SWHSTW)) and river waters and sediment (Shan Pui River and Ng Tung River) within the Mai Po Ramsar site in Hong Kong SAR, China. In both STWs, Pb had the highest removal efficiencies (YLSTW 86.5 ± 19.0% to 97.3 ± 3.04%; SWHSTW 87.4 ± 12.8% to 100 ± 0.0800%). In the whole effluent toxicity test, both STWs were effective in lowering the toxicity of the effluent to zebrafish and cherry shrimp. The environmental risk assessments of these HMs on three local aquatic organisms, three species of fish, two species of crustaceans, and three species of algae, were calculated based on measured HMs concentrations in river water and sewage samples, and the predicted no-effect concentrations. Results showed that Zn concentrations in all collected samples posed potential risks to all studied aquatic organisms (average risk quotient = 445). The concentrations of Cu in the rivers posed potential risks (average risk quotient = 5.42) to all fish species. It was concluded that Zn and Hg derived from the STWs might pose potential risks to the living organisms inhabiting the Ramsar site, and Cu, Cd, Pb, and As in the rivers were originated from the two rivers and possibly other tributaries.

Profiles and removal efficiency of polycyclic aromatic hydrocarbons by two different types of sewage treatment plants in Hong Kong.

Sewage discharge could be a major source of polycyclic aromatic hydrocarbons (PAHs) in the coastal waters. Stonecutters Island and Shatin Sewage Treatment Works (SCISTW and STSTW) in Hong Kong, adopted chemically enhanced primary treatment and biological treatment, respectively. This study aimed at (1) determining the removal efficiencies of PAHs, (2) comparing the capabilities in removing PAHs, and (3) characterizing the profile of each individual PAHs, in the two sewage treatment plants (STPs). Quantification of 16 PAHs was conducted by a Gas Chromatography. The concentrations of total PAHs decreased gradually along the treatment processes (from 301±255 and 307±217ng/L to 14.9±12.1 and 63.3±54.1ng/L in STSTW and SCISTW, respectively). It was noted that STSTW was more capable in removing total PAHs than SCISTW with average total removal efficiency 94.4%±4.12% vs. 79.2%±7.48% (p<0.05). The removal of PAHs was probably due to sorption in particular matter, confirmed by the higher distribution coefficient of individual and total PAHs in solid samples (dewatered sludge contained 92.5% and 74.7% of total PAHs in SCISTW and STSTW, respectively) than liquid samples (final effluent-total contained 7.53% and 25.3% of total PAHs in STSTW and SCISTW, respectively). Despite the impressive capability of STSTW and SCISTW in removing PAHs, there was still a considerable amount of total PAHs (1.85 and 39.3kg/year, respectively for the two STPs) being discharged into Hong Kong coastal waters, which would be an environmental concern.

Applications of charcoal, activated charcoal, and biochar in aquaculture - A review.

Environmental pollution and poor feed quality pose potential threats to aquatic organisms and human health, representing challenges for the aquaculture industry. In light of the rising demand for aquatic organisms, there is an urgent need to improve aquacultural production and protect the products from contamination. Char, a carbonaceous material derived through pyrolysis of organic carbon-rich biomass, has proven advantages in soil, air, and water remediation. While char's performance and the associated physicochemical characteristics depend strongly on the pyrolysis temperature, residence time, and feedstock type, char generally shows advantages in pollutant removal from the environment and livestock. This enables it to enhance the health and growth performance of livestock. Given the growing attention to char application in aquaculture in recent years, this review summarises major studies on three applications: aquacultural water treatment, sediment remediation, and char-feed supplement. Most of these studies have demonstrated char's positive effects on pollutant removal from organisms and aquacultural environments. Moreover, adopting char as fish feed can improve fish growth performance and the condition of their intestinal villi. However, due to insufficient literature, further investigation is needed into the mechanistic aspects of pollutants removal in aquatic organisms by char as a feed additive, such as the transportation of char inside aquatic organisms, the positive and negative effects of char on these products, and how char alters the gut microbiota community of these products. This paper presents an overview of the current application of char in aquaculture and highlights the research areas that require further investigation to enrich future studies.

Mutagenicity and genotoxicity of Hong Kong soils contaminated by polycyclic aromatic hydrocarbons and dioxins/furans.

The aim of this study was to evaluate mutagenicity and genotoxicity of soils from 12 different land use types such as electronic waste dismantling workshop, open burning site and car dismantling workshop (CDW), based on soil concentrations of polycyclic aromatic hydrocarbons (PAHs), and polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs). Soils of CDW contained the sum of 10 PAHs level (94392µg/kg) exceeded The New Dutch List (Dutch Intervention Value (40000µg/kg)), dominated by high molecular PAHs (99.6%) and benzo(a)pyrene (82.6%), indicating its potential carcinogenic risks. In addition, Ames test and SOS Chromotest further manifested that soil of CDW had a significantly higher mutagenic potency (MP) of 13.8 and 7.43 on both strains of TA98 and TA100 with S9 mix, respectively, and a relatively higher genotoxicity with S9 mix (SOS inducing potency=1.16), amongst the 12 different soil types. BaP TEQ PAHs in soils were significantly correlated with MP of TA98, with and without S9 mix (r=0.858 and r=0.976 at p<0.01); MP of TA100 with and without S9 mix (r=0.666 at p<0.05 and r=0.819 at p<0.01); and SOSIP of Escherichia coli PQ 37 with S9 mix (r=0.693 at p<0.05), accordingly. Soils of CDW possessed a higher carcinogenic risk (mutagenicity and genotoxicity), based on PAHs concentrations. Bioremediation is recommended to treat the contaminated soils.

Characterizing the optimal operation of photocatalytic degradation of BDE-209 by nano-sized TiO2.

Brominated flame retardants have been widely used in industry. There is a rapid growing public concern for their availabilities in the environment. Advanced oxidation process (AOP) is a promising and efficient technology which may be used to remove emerging chemicals such as brominated flame retardants. This study aims at investigating optimal operational conditions for the removal of BDE-209 using nano-scaled titanium(IV) oxide. The residual PBDE congeners after photocatalytical degradation of BDE-209 by TiO2 were analysed by gas chromatography-mass spectrometry (GC-MS). It was found that the degradability of BDE-209 by TiO2 was attributed to its photocatalytic activity but not the small size of the particles. The half-life of removing BDE-209 by TiO2 was 3.05 days under visible light. Tetra- and penta-BDEs were the major degraded products of BDE-209. Optimum conditions for photocatalytical degradation of BDE-209 was found to be at pH 12 (93% +/- 1%), 5, 10, 20 mg/L (93.0% +/- 1.70%, 91.6% +/- 3.21%, 91.9% +/- 0.952%, respectively), respectively of humic acid and in the form of anatase/rutile TiO2 (82% +/- 3%). Hence, the efficiency of removing BDE-209 can be maximized while being cost effective at the said operating conditions.

Using food waste to cultivate safe, good-quality Sabah (giant hybrid) grouper: Dioxins and dioxin-like polychlorinated biphenyls.

Dioxins and dioxin-like polychlorinated biphenyls (dl-PCBs) in fish fillet counteract the health benefits of fish products. In this study, food waste was used as a protein alternative to replacing fishmeal commonly used in the commercial fish feed, aiming to cultivate Sabah grouper with acceptable levels of dioxins and dl-PCBs. The concentrations of dioxins and dl-PCBs, as well as the fish growth performance, were compared between the fish groups fed with food waste-based feed (FWBF) and commercial feed (Nanyu®, control). The results showed that the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) (1.22 pg/g dry weight (d.w.)) and non-ortho-dl-PCBs (13.0 pg/g d.w.) were significantly lower (p < 0.05) in the FWBF than in the control feed (commercial feed) (PCDDs: 2.35 pg/g d.w.; non-ortho-dl-PCBs: 27.2 pg/g d.w.). The growth performance of the fish group fed with the FWBF was comparable to that fed with the control feed. There were no significant differences between the WHO2005-TEQ values of different fish fillets (1.00, 1.11, and 1.10 pg WHO2005-TEQ/g d.w. for FWBF group, control feed group, and local market fish, respectively). Based on the guidelines provided by European Food Safety Authority (ESFA) and U.S. Environmental Protection Agency (USEPA), the fish fed with the FWBF were safe for human consumption (hazard index values: 0.284-0.522; cancer risk range: 2.59-2.97 × 10-5). The findings of this study suggest that food waste could serve as an alternative protein source for cultivating Sabah grouper with acceptable levels of dioxins and dl-PCBs.

Environmental health impacts of microplastics exposure on structural organization levels in the human body.

The ubiquitous prevalence of microplastics pollution has raised concerns about microplastics' potential risks and impacts on the global environment. However, the potential human health risks and impacts of microplastics remain largely unexplored. By providing an overview regarding the interaction of microplastics and human health, this review extends current knowledge on the potential impacts of microplastics pollution on humans from an environmental health perspective. The paper firstly presents the characteristics of microplastics as well as the status of global microplastics pollution. As for human health, the potential hazards of microplastics are reflected by toxic chemical components, vectors of contaminants, and physical damage. Extensive microplastic pollution on ecosystems due to human activities leads to inevitable human exposure, which may occur by dietary, inhalation and/or skin contact. Accordingly, microplastics exposure is closely associated with human health. This study explores the potential interactions of microplastics with the biological organization at various levels, including chemical, cellular, tissue, organ, and system levels. The review concludes by highlighting five urgent perspectives and implications for future research on microplastics: 1) Developing a standard terminology and research methods; 2) Reinforcing microplastics pollution governance; 3) Exploring innovative strategies and technologies; 4) Engaging the public and change behaviour; and 5) Adopting a transdisciplinary approach.

Health risk assessment of organochlorine pesticides with emphasis on DDTs and HCHs in abandoned agricultural soils.

The aim of this study was to evaluate the consequence of changing land use from agriculture land to other use purposes with respect to OCPs non-cancer and cancer risk on human health, based on concentrations of DDTs and HCHs in soils collected from 55 locations representing 12 different land use types. There were no non-cancer risks of DDTs and γ-HCHs on adults and children, and there were very low cancer risks of DDD, o,p'-DDE, DDT, α-HCH, ß-HCH, γ-HCH based on their total concentrations in all samples. Nonetheless, there were significant correlations of DDT to its metabolites (DDE and DDD) (r = 0.506 and r = 0.648) and DDE to DDD (r = 0.438) both at p < 0.01. OCP levels should be routinely monitored in different environmental media and food in order to verify whether there is fresh input. Their potential risks on human health should also be assessed.

Protecting water birds of wetlands: Using toxicological tests and ecological risk assessment, based on metal/loid (s) of water, sediment and biota samples.

Water, sediment and biota (two fish and one shrimp species) samples were collected from rivers, ponds, mudflat and estuaries within the Mai Po Ramsar site in Hong Kong, China, to determine the concentrations of heavy metals/loid (HMs): cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb), zinc (Zn), and arsenic (As). The mutagenicity and toxicity of water and sediment samples were evaluated using Ames test and Microtox® bioassay, respectively. Ecological risk assessments on water birds were also conducted based on HM concentrations in biota, sediment and water samples. In general, results showed that downstream of Shan Pui River and Ng Tung River had relatively higher HM concentrations (e.g. Cu: 0.992-9.49 µg/L; As: 0.342-5.83 µg/L) when compared with estuaries (Cu: 0.400-3.69 µg/L; As: 0.220-0.931 µg/L) and ponds (Cu: 0.0402-2.41 µg/L; As: 0.0501-2.10 µg/L), except Hg and Cd. On the other hand, sediment samples collected from Ng Tung River showed mutagenicity on Salmonella typhimurium tester strain TA100, while the mudflat samples had mutagenicity on tester strain TA98 used in the Ames tests. Microtox® bioassay indicated that only sediment of Ng Tung River showed acute toxicity with a 15 min half maximal effective concentration (EC50) value of 30.5%. Results of ecological risk assessments showed that grey heron (Ardea cinerea), which feeds on fish and shrimps at Shan Pui River and ponds were not at risk. However, common sandpiper (Actitis hypoleucos), which feeds at ponds were subjected to a potential health risk due to its behavior of seeking food from the sediments, especially this bird species has a small body size. This indicates juvenile birds of other species may also be affected. Remediation should be implemented to relief the potential risk of Cu and Pb, to these water birds in the Mai Po Ramsar site.

Potential sources and associated risk assessment of potentially toxic elements in paddy soils of a combined urban and rural area.

The contamination of combined urban and rural area is a growing environmental issue due to rapid industrialization in China. This study investigated the eight potentially toxic elements (PTEs) arsenic (As), lead (Pb), cadmium (Cd), mercury (Hg), chromium (Cr), copper (Cu), nickel (Ni), and zinc (Zn) in paddy fields in a combined urban and rural area in Shaoxing city, Zhejiang province. Concentrations of the PTEs were determined in 60 topsoil samples (0-20 cm) collected from paddy fields in a combined urban and rural area in Shaoxing city, Zhejiang province, southeast China. The average contents of Pb, Cu, Zn, Cd, Hg, and As in the paddy soils increased by 23.7, 6.9, 17.0, 79.8, 62.5, and 47.9%, respectively, relative to their corresponding natural background concentrations. The mean contents of Cr and Ni did not exceed their background values. Multivariate statistical and geostatistical methods were used to distinguish between the PTEs (Cd, As, Pb, Zn, and Hg) contaminating the soils of the study area from those (Cr, Cu, and Ni) at background concentrations. About 17.2% of the soils were moderately polluted with PTEs as a result of urbanization. The results may be useful to policy makers in agricultural and urban management.

Fate of bisphenol A, perfluorooctanoic acid and perfluorooctanesulfonate in two different types of sewage treatment works in Hong Kong.

This study aimed at investigating the removal efficiencies of perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS) and bisphenol A (BPA) of two major sewage treatment works in Hong Kong: Stonecutters Island STW (SCISTW) which adopts chemically enhanced primary treatment (CEPT) process and Sha Tin STW (STSTW) which employs biological treatment. Liquid portion (LP) and particulate matter (PM) of liquid sewage samples and sludge samples were collected and followed by liquid chromatograph system. It was found that BPA (44.6 ± 35.1%) generally achieved higher TRE than the two other chemicals (PFOS (-18.8 ± 34.8%) and PFOA (-104 ± 86.8%)) in STSTW (p < 0.05). Most of the PFOA, PFOS and BPA was discharged through final effluent (PFOA: 95.6 ± 1.00% and 94.5 ± 3.13%; PFOS: 77.7 ± 1.48% and 72.6 ± 6.07%; BPA: 99.2 ± 0.950% and 92.8 ± 7.25%, respectively) rather than stored in the sludge/cake (PFOA: 4.45 ± 1.00% and 5.47 ± 3.13%, PFOS: 22.3 ± 1.48% and 27.4 ± 6.07%, BPA: 0.844 ± 0.950% and 7.20 ± 7.25%, respectively). After the sewage purification process, the two STW released considerable amounts of PFOA, PFOS and BPA in the final effluent (PFOA: 0.638 ± 0.227 kg/year; PFOS: 0.409 ± 0.126 kg/year; BPA: 10.4 ± 3.83 kg/year in STSTW; PFOA: 3.08 ± 1.415 kg/year; PFOS: 2.13 ± 0.452 kg/year; BPA: 714 ± 768 kg/year in SCISTW) and in the sludge (PFOA: 0.0360 ± 0.0250 kg/year; PFOS: 0.149 ± 0.00100 kg/year; BPA: 1.09 ± 1.47 kg/year in STSTW; PFOA: 0.139 ± 0.0670 kg/year; PFOS: 0.606 ± 0.0780 kg/year; BPA: 3.05 ± 3.95 kg/year in SCISTW). This study may help to provide crucial information for further development of municipal sewage system in treating synthetic emerging chemicals.

Removal of decabromodiphenyl ether (BDE-209) using a combined system involving TiO2 photocatalysis and wetland plants.

There is a rising concern about the capability of sewage treatment works in treating emerging chemicals, such as polybrominated diphenyl ethers (PBDEs). A combined photocatalysis (TiO2 and visible light) and constructed wetland system (planted with Oryza sativa (rice cultivar: Hefengzhan) and Phragmites australis (common reed)) was designed to study PBDEs removal efficiencies. After the pre-treatment in TiO2 suspension, the artificially BDE-209 spiked sewage (78.2 and 782nmol/L) was discharged into the sub-surface flow constructed wetland tanks planted with rice and common reed, respectively. The treated sewage, soil, plant roots, shoots, rice grains and hulls were collected and analyzed for PBDEs by GC-MS. The removals of BDE-209 in the combined systems (93.6±2.19% (78.2nmol/L) and 92.1±1.11% (782nmol/L)) were significantly higher than those in the photocatalytic systems (56.3±5.78% (78.2nmol/L) and 54.7±9.47% (782nmol/L)), which could be explained by the enhanced biodegradability of PBDEs in photocatalysis, led to its better dissipation by rice plants. Therefore, this combined system might help to degrade BDE-209 in the wastewater effluent, reducing its potential entry into aquatic food chains.

A pilot study on health risk assessment based on body loadings of PCBs of lactating mothers at Taizhou, China, the world's major site for recycling transformers.

Our early study reported an extraordinarily high Estimated Daily Intake (EDI) of PCBs of lactating mothers from Taizhou, Zhejiang Province, China (based on a food consumption survey and food basket analysis). The EDI well exceeded the intake limit stipulated by FAO/WHO 70 pg TEQ/kg body weight (bw)/month. The present pilot study provided further information on PCBs body burden in lactating mothers of Taizhou. The total PCBs detected in human milk, placenta and hair samples of these lactating mothers were 363 ng/g lipid, 224 ng/g lipid, and 386 ng/g dry wt. Respectively, three times higher than those samples collected from the reference site (Lin'an). Compared with the previous reported values in the 3rd WHO coordinated study, Taizhou topped the list of 32 countries/regions with regards to WHO-PCB-TEQ values of milk samples, which could be attributed to the relatively higher level of PCB-126 derived from electronic waste. In addition, the corresponding EDI of PCBs of Taizhou mothers (12.9 pg WHO-PCB-TEQ/kg bw/day) and infants (438 pg WHO-PCB-TEQ/kg) were derived from individual congener levels in human milk. The results were also higher than the tolerable daily intakes recommended by WHO (1-4 pg WHO-TEQ/kg bw/day) by 3 and 110 times, for mothers and infants, respectively. A more intensive epidemiological study on the potential health effects of e-waste recycling activities affecting both workers and residents seems to be of top priority, based on findings of this pilot study.

Uptake and transport mechanisms of decabromodiphenyl ether (BDE-209) by rice (Oryza sativa).

The extensive industrial use of brominated flame retardants has aroused rapidly growing public concerns about their ubiquity in the environment. The feasibility of uptake and translocation of decabromodiphenyl ether (BDE-209) by three rice cultivars, namely Fengmeizhan, Hefengzhan and Guangyinzhan, and the uptake mechanisms of BDE-209 into rice roots, were investigated by employing a partition-limited model. Uptake of BDE-209 by the rice cultivars (Fengmeizhan, Hefengzhan and Guangyinzhan) was examined by a 60-day cultivation in sterilized BDE-209 spiked sand, followed by Soxhlet extraction and gas chromatography-mass spectrometry (GC-MS) analysis. A partition-limited model was applied for estimating and describing the approach of the uptake of BDE-209 by rice in sand. The average quasi-equilibrium factor (αpt) of BDE-209 in root uptake in sand was 0.112×10(-3) for three rice cultivars in the present study (<1), implying a non-equilibrium movement of molecules and a dominated passive transport uptake. According to the results of sorption analysis of dead and fresh roots, apoplastic pathway likely dominated the transport of BDE-209 into roots cells.

Profiles and removal efficiency of polybrominated diphenyl ethers by two different types of sewage treatment work in Hong Kong.

This study was to investigate removal efficiencies and profiles of 14 polybrominated diphenyl ether (PBDE) congeners by two different types of sewage treatment work (STW) in Hong Kong: Stonecutters Island STW (SCISTW) which uses chemically enhanced primary treatment (CEPT) process and Sha Tin STW (STSTW) which adopts biological treatment. The results indicated that both SCISTW and STSTW had a high total removal efficiency for BDE-47, BDE-99 BDE-209 and total PBDEs (SCISTW: 71.6 ± 15.8, 84.7 ± 12.3, 96.0 ± 2.62 and 87.4 ± 8.02%, respectively; STSTW: 74.8 ± 9.5, 90.7 ± 9.14, 96.2 ± 2.41 and 89.3 ± 2.62%, respectively) and PBDEs were chiefly removed by sorption. However, the profile of PBDEs demonstrated that the relative proportions of BDE-28 and BDE-47 in total PBDEs markedly increased, while that of BDE-209 decreased in the effluent samples of the two sewage treatment works, especially in STSTW. The percentage of BDE-209 in total PBDEs in effluent (49.3%) of SCISTW was 21.2% lower than that in influent (70.5%), and the percentage of BDE-209 in total PBDEs in effluent (13.8%) of STSTW was 34.1% reduced from influent (47.9%). Despite overall removal, the percentage of BDE-47 in total PBDEs in effluent (17.6%) of SCISTW was 6.85% higher than that in influent (10.7%), and the percentage of BDE-47 in total PBDEs in effluent (33.5%) of STSTW was 18.1% increased from influent (16.8%). The increase in proportion of BDE-47 in the effluent might raise environmental and public health concerns. Our study is a first attempt in reporting the PBDE congener profiles in different phases of sewage treatment.

Human health risk assessment of soil dioxin/furans contamination and dioxin-like activity determined by ethoxyresorufin-O-deethylase bioassay.

The major objective of this study was to evaluate the human health risks of agricultural land use conversion to other purposes in Hong Kong, based on the levels of polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (PCDD/Fs) and determined dioxin-like activity in soil using ethoxyresorufin-O-deethylase (EROD) bioassay. Hazard quotient showed soils of open burning site (OBS) and electronic waste open burning site (EW (OBS)) exert a relatively higher non-cancer risk on adults (50.9 and 8.00) and children (407 and 64.0) via the pathway of accidental ingestion of soil particles than other types of land use. In addition, the levels of 17 PCDD/Fs congeners in OBS and EW (OBS) soils indicated high and moderate (1654 and 260 in one million people) cancer risks through the above pathway. Furthermore, the biologically derived TCDD concentrations (TEQbio) were also significantly correlated to the chemically derived toxic equivalent concentrations of dioxin-like chemicals (TEQcal (sum of chemically derived 2,3,7,8-TeCDD toxic equivalent concentrations (TEQPCDD/F) and chemically derived dioxin-like PAHs toxic equivalent concentrations (TEQPAH)) (r = 0.770, p <0.05). PCDD/Fs (95.4 to 99.9%) were the major stressor to the TEQcal in the soil samples, indicating higher concentrations of PCDD/Fs derived from chemical analyses may reflect a higher potency of inducing EROD activity.

Cancer risk assessments of Hong Kong soils contaminated by polycyclic aromatic hydrocarbons.

The aim of this study was to evaluate soils from 12 different land use types on human cancer risks, with the main focus being on human cancer risks related to polycyclic aromatic hydrocarbons (PAHs). Fifty-five locations were selected to represent 12 different types of land use (electronic waste dismantling workshop (EW (DW)); open burning site (OBS); car dismantling workshop (CDW) etc.). The total concentrations of 16 PAHs in terms of total burden and their bioaccessibility were analysed using GC/MS. The PAHs concentrations were subsequently used to establish cancer risks in humans via three exposure pathways, namely, accident ingestion of soil, dermal contact soil and inhalation of soil particles. When the 95th centile values of total PAH concentrations were used to derive ingestion and dermal cancer risk probabilities on humans, the CDW land use type indicated a moderate potential for cancerous development (244 × 10(-6) and 209 × 10(-6), respectively). Bioaccessible PAHs content in soil samples from CDW (3.60 × 10(-6)) were also classified as low cancer risk. CDW soil possessed a higher carcinogenic risk based on PAH concentrations. Bioremediation is recommended to treat the contaminated soil.

Cancer risk assessment of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in former agricultural soils of Hong Kong.

The major objective of this study was to evaluate the carcinogenic risk posed to humans through PBDEs and PCBs of changing agricultural land use for recycling of e-waste and open burning of municipal waste. Nine locations were selected to represent 6 different types of land use such as e-waste dismantling workshop (EW (DW)) and e-waste open burning site (EW (OBS)). The total concentrations for PBDEs and PCBs, and the bioaccessibility of PCBs were determined using Soxhlet extraction and in vitro simulated gastric solution, respectively. Both total and bioaccessible concentrations were subsequently used to establish the cancer risk probabilities in humans via ingestion, dermal contact and inhalation of soil particles. It was found that very low cancer risk in all 6 types of different land use was caused by BDE-209. Nevertheless, at the 95th centile, the concentration of PCBs in EW (DW) and EW (OBS) indicate a low cancer risk to humans of 40 and 2.1 in a million, respectively, while the same was also observed for the bioaccessible PCBs in EW (DW) of 1.71 ± 2.96 in a million.