Yoshitaka Imaizumi

Spatial, phase, and temporal distributions of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) in Tokyo Bay, Japan.

The spatial distribution, partitioning, and time trends of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) were investigated in the water column and bottom sediment of Tokyo Bay, Japan, during 2004-2006. A total of 480 water and 60 sediment samples obtained by regular 20-station samplings ascertained the three-dimensional distributions of these compounds and changes in the seawater structure in the whole bay. The median of volume-based average water-borne concentrations of PFOS and PFOA was 3.7 and 12 ng/L, respectively. The median concentrations in sediment were 0.61 (PFOS) and 0.20 (PFOA) ng/g-dry. Vertical mixing of the water column probably affected the vertical distribution of these compounds. The negative correlations between PFOS and PFOA concentrations and water salinity and the horizontal distributions of their concentrations suggested that freshwater inputs into the bay were the source of these compounds. A mixing model estimated the average PFOS concentration in the freshwater inputs to be 29 ng/L. The common logarithm of the partition coefficients between the dissolved and suspended-particle-sorbed phases varied among samples, with the average of 4.2 (PFOS) and 3.5 (PFOA). Our analyses indicated no apparent time trends in the concentrations of these compounds during 2004-2006 in either the freshwater input or the bay.

Spatial distribution and partitioning of polychlorinated biphenyls in Tokyo Bay, Japan

Spatial distributions and partitioning of polychlorinated biphenyls (PCBs) in Tokyo Bay, Japan, were evaluated by measuring the concentrations of all 209 PCB congeners in surface and bottom waters and bottom sediment at 10 locations. The dissolved + particulate summed congener concentrations (SigmaPCB [sum of the concentrations of all 209 PCB congeners]) in surface and bottom waters ranged from 120 to 1100 pg L(-1) (median 250 pg L(-1)) and from 83 to 910 pg L(-1) (median 230 pg L(-1)), respectively. The concentrations did not statistically differ between the two layers, possibly because of vertical mixing of the water column. SigmaPCB concentrations in sediment ranged from 2.7 to 110 ng g(-1)-dry weight. The highest SigmaPCB concentrations in both water and sediment were found at stations in the northern bay. Logarithms of field-observed organic carbon-normalized partition coefficients (K(OC)) increased linearly as the log octanol-water partition coefficients (K(OW)) increased, up to a log K(OW) of about 6.5, and then decreased for log K(OW) > 6.5 (mostly hexa- and hepta-chlorinated biphenyls). Furthermore, log K(OC) values of congeners having log K(OW) < 6.5 were higher by about 1 than values predicted by a published empirically derived equation, suggesting that application of K(OC) values determined in laboratory experiments with soil or sediment samples to fate prediction models may result in overestimation by about one order of magnitude of the concentrations of PCBs with log K(OW) < 6.5 in the dissolved phase in the water column.

Temporal trends for inflow of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) to Tokyo Bay, Japan, estimated by a receptor-oriented approach.

We estimated inflow rates of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) to Tokyo Bay, Japan, between February 2004 and February 2011 by a receptor-oriented approach based on quarterly samplings of the bay water. Temporal trends in these inflow rates are an important basis for evaluating changes in PFOS and PFOA emissions in the Tokyo Bay catchment basin. A mixing model estimated the average concentrations of these compounds in the freshwater inflow to the bay, which were then multiplied by estimated freshwater inflow rates to obtain the inflow rates of these compounds. The receptor-oriented approach enabled us to comprehensively cover inflow to the bay, including inflow via direct discharge to the bay. On a logarithmic basis, the rate of inflow for PFOS decreased gradually, particularly after 2006, whereas that for PFOA exhibited a marked stepwise decrease from 2006 to 2007. The rate of inflow for PFOS decreased from 730kg/y during 2004-2006 to 160kg/y in 2010, whereas that for PFOA decreased from 2000kg/y during 2004-2006 to 290kg/y in 2010. These reductions probably reflected reductions in the use and emission of these compounds and their precursors in the Tokyo Bay catchment basin. Our estimated per-person inflow rates (i.e., inflow rates divided by the estimated population in the basin) for PFOS were generally comparable to previously reported per-person waterborne emission rates in Japan and other countries, whereas those for PFOA were generally higher than previously reported per-person waterborne emission rates. A comparison with previous estimates of household emission rates of these compounds suggested that our inflow estimates included a considerable contribution from point industrial sources.

Towards modelling of the environmental fate of pharmaceuticals using the QSPR-MM scheme

Pharmaceuticals are considered as a new, important group of pollutants. These compounds can enter the environment via several routes and can disturb the natural balance of ecosystems. Factors affecting the environmental fate of medical substances can be determined with computational modelling. The routine application of the modelling methodology in the environmental risk assessment for newly designed pharmaceuticals would enable prediction of their important physical/chemical properties and forecasting their long-range transport and fate. In this contribution, we present the existing state-of-the-art and review the currently available modelling tools of two groups: Quantitative Structure-Property Relationship techniques and Multimedia Mass-balance models. We discuss the current research needs in the context of extending the applicability of the existing tools onto pharmaceuticals, being a more structurally diversified group of contaminants than persistence organic pollutants, for which the majority of the existing models have been originally developed. Multimedia fate models applied for pharmaceuticals are reviewed.QSPR approach to predict physical/chemical properties of pharmaceuticals is reviewed.QSPR-MM combined model is suggested to predict Pov and LRTP of chemical pollutants.

Dietary uptake kinetics of polychlorinated biphenyls from sediment-contaminated sandworms in a marine benthic fish (Pseudopleuronectes yokohamae).

To evaluate the dietary uptake of polychlorinated biphenyls (PCBs) from live food, we investigated the dietary uptake and depuration kinetics of PCBs in a marine benthic fish (marbled sole, Pseudopleuronectes yokohamae) by using as food live sandworms (Perinereis nuntia) that were laboratory-exposed to field-collected PCB-contaminated sediment. Marbled sole were fed the PCB-contaminated sandworms for 28d and then uncontaminated sandworms for 56d. The assimilation efficiencies (AEs) of 84 PCB congeners via the gastrointestinal tract (GIT) to the muscle of the fish ranged from 0.21 to 0.78; whole-body AEs would be lower than those of muscle because of the lower PCB concentrations, on a lipid basis. The AEs determined in this study were lower than those in other studies that used PCB-spiked commercial pelletized food. The lower AEs found in this study might be attributable to differences in the food administered (live sandworms vs. commercial pellet food), possibly because of low digestibility of sandworm lipids by marbled sole. In addition, the AEs in this study tended to increase with increasing log octanol-water partition coefficients (K(OW)) up to about seven, although AEs in the other studies using commercial pelletized food did not increase with increasing logK(OW). This result suggests the co-transport of highly hydrophobic PCB congeners along with lipids and fatty acids from the digested sandworms into the GIT epithelium cells. The growth-corrected half-lives of 26 PCB congeners in the muscle of fish ranged from 20 to 107d.

Particle-size-fractioned transfer of dioxins from sediments to water columns by resuspension process

Particle-size-fractioned transfer of dioxins from sediments to water columns by resuspension process was investigated, using supernatant samples obtained from shaking experiments of sediment-water pairs simulating natural disturbances. The concentrations (dry-matter mass basis) of individual compounds (C(fraction)) in two particle size fractions (0.1-1 and 1-10 microm) in the supernatants were generally slightly higher than those in the original sediment (C(sed)). C(fraction)/C(sed) ratios ranged from 0.45 to 5.9 (median 1.5) without consistent differences among congener groups or consistent correlations against the number of chlorine atoms. The dioxin concentrations in the water column associated with the remaining sediment particles can therefore be estimated by those in the original sediment and by the concentration of suspended sediment particles in the water. The concentration of each compound in the remaining sediment particles (mostly 0.1-10 microm in size) can be roughly estimated by multiplying the concentration in the original sediment by 1.5.

Transfer kinetics of perfluorooctane sulfonate from water and sediment to a marine benthic fish, the marbled flounder (Pseudopleuronectes yokohamae)

The authors investigated the kinetics of transfer of perfluorooctane sulfonate (PFOS) from water, suspended sediment, and bottom sediment to a marine benthic fish, the marbled flounder (Pseudopleuronectes yokohamae). Fish were exposed in 3 treatments to PFOS in combinations of these exposure media for 28 d and then depurated for 84 d. A major part (37–66%) of PFOS in the fish was in the carcass (i.e., whole body minus muscle and internal organs). Three first-order-kinetic models that differed in exposure media, that is, 1) sum of dissolved and particulate phases and sediment; 2) dissolved phase, particulate phase, and sediment; and 3) dissolved phase only, were fitted to the data assuming common rate constants among the treatments. The uptake efficiency of dissolved PFOS at the respiratory surfaces was estimated to be 3.2% that of oxygen, and the half-life of PFOS in the whole body to be 29 d to 31 d. The better fit of models 1 and 2 and the values of the estimated uptake rate constants suggested that the PFOS in suspended and bottom sediments, in addition to that dissolved in water, contributed to the observed body burden of the fish. Based on an evaluation of several possible contributing factors to the uptake of PFOS from suspended and bottom sediments, the authors propose that further investigation is necessary regarding the mechanisms responsible for the uptake. Environ Toxicol Chem 2013;32:2009–2017.

Ecological risk assessment of herbicides in Japan: Integrating spatiotemporal variation in exposure and effects using a multimedia model and algal density dynamics models

Application of herbicides to paddy fields in Japan has strong seasonality, and their environmental concentrations exhibit clear spatiotemporal variation. The authors developed an approach that combines a multimedia environmental exposure model (Grid-Catchment Integrated Modeling System) and density dynamics models for algae. This approach enabled assessment of ecological risk when the exposure concentration shows spatiotemporal variation. First, risk maps of 5 herbicides (pretilachlor, butachlor, simetryn, mefenacet, and esprocarb) were created from the spatial predictions of environmental concentrations and 50% inhibitory concentrations of the herbicides. Simulations of algal density dynamics at high-risk sites were then conducted by incorporating the predicted temporal dynamics of the environmental concentration of each herbicide at the sites. The results suggested that the risk of pretilachlor was clearly the highest of the 5 herbicides, in terms of both the spatial distributions and the temporal durations. The present study highlights the importance of integrating exposure models and effect models to clarify spatial and temporal risk and to develop management plans for chemical exposure that shows high spatiotemporal variation.

Estimation of long-term dietary exposure to acrylamide of the Japanese people

ABSTRACT Acrylamide is a probable human carcinogen and known human neurotoxin. This study estimated hypothetical long-term dietary exposure to acrylamide of the Japanese people using probabilistic and deterministic approaches by combining the concentration of acrylamide in foods with the amount and frequency of food consumption in the population. Data included acrylamide concentrations in more than 2400 individual food samples from a national survey and the literature from 2004 to 2013. Food consumption amounts were derived from the data of 24,293 Japanese citizens aged 1 year and older in the 2012 National Health and Nutrition Survey. Median lifetime average dietary exposure to acrylamide was estimated as 147–154 ng/kg body weight (bw)/day (95th percentile, 226–261 ng/kg bw/day). The deterministic estimate of lifetime exposure was 158 ng/kg bw/day and ranged from 119 ng/kg bw/day for the period of life after 60 years old to 409 ng/kg bw/day for the period between 1 and 6 years old. This study found that vegetables cooked at a high temperature, coffee and cooked potato were the major food groups contributing to long-term dietary acrylamide exposure of the Japanese people.