Keiji Okuda’s research while affiliated with Tokyo University of Agriculture and Technology and other places

The tsunami caused by the Great East Japan Earthquake on March 11, 2011 disturbed coastal environments in the eastern Tohoku region in Japan. Numerous terrestrial materials, including anthropogenic organic compounds, were deposited in the coastal zone. To evaluate the impacts of the disaster, we analyzed PCBs, LABs, PAHs, and hopanes in mussels collected from 12 locations in the east of Tohoku during 2011-2015 (series A) by GC-ECD or GC-MS and compared them with results from mussels collected from 22 locations around Japan during 2001-2004 (series B). Early LAB concentrations in series A at some locations were higher than the maximum concentrations in series B but decreased during the 5 years. Because LABs are molecular markers for sewage, these decreases are consistent with the recovery of sewage treatment plants in these areas. Early PAH concentrations at several locations were higher than the maximum concentrations in series B but also decreased. These high concentrations would have been derived from oil spills. The decreases of both LABs and PAHs indicate that these locations were affected by the tsunami but recovered. In contrast, later high concentrations of target compounds were detected sporadically at several locations. This pattern suggests that environmental pollution was caused by human activities, such as reconstruction. To understand the long-term trend of environmental pollution induced by the disaster, continuous monitoring along the Tohoku coast is required.

Samples of polyethylene pellets were collected at 30 beaches from 17 countries and analyzed for organochlorine compounds. PCB concentrations in the pellets were highest on US coasts, followed by western Europe and Japan, and were lower in tropical Asia, southern Africa and Australia. This spatial pattern reflected regional differences in the usage of PCBs and was positively correlated with data from Mussel Watch, another monitoring approach. DDTs showed high concentrations on the US west coast and in Vietnam. In Vietnam, DDT was predominant over its metabolites (DDE and DDD), suggesting the principal source may be current usage of the pesticide for malaria control. High concentrations of pesticide HCHs were detected in the pellets from southern Africa, suggesting current usage of the pesticides in southern Africa. This study demonstrates the utility and feasibility of the International Pellet Watch approach to monitor POPs at a global scale.

Thirteen isomers of branched para-nonylphenols (para-NP) in three technical mixtures were isomer-specifically determined using their synthesized standards by SIM of structurally specific ions, m/z 135, 149 or 163 with GC-MS. Of the 13 isomers, four isomers, 4-(2,4-dimethylheptan-4-yl)phenol, 4-(4-methyloctan-4-yl)phenol, 4-(3-ethyl-2-methylhexan-2-yl)phenol (3E22NP) and 4-(2,3-dimethylheptan-2-yl)phenol synthesized for their determinations were first used as standard substances. The 13 isomers in the technical mixtures individually occurred at mass percent portion of more than 2%. The total mass percent portions in the mixtures from Tokyo Chemical Industry (TCI), Aldrich, and Fluka covered with 89+/-2%, 75+/-4% and 77+/-2%, respectively. The abundance of 4-(3,6-dimethylheptan-3-yl)phenol in the three mixtures was the largest with 11.1+/-2% to 9.9+/-0.3%, while that of 4-(2-methyloctan-2-yl)phenol was the smallest with 2.9+/-0.3% to 3.0+/-0.2%. Additionally, structures of four new isomers of more than 1% portion present in a technical mixture were elucidated as two pairs of diastereomeric isomers: two types of 4-(3,4-dimethylheptan-4-yl)phenol (344NP) and those of 4-(3,4-dimethylheptan-3-yl)phenol (343NP). By estrogenic assay of 13 isomers with yeast estrogen screen system, the activity of 3E22NP was the highest, while that of 4-(3-methyloctan-3-yl)phenol was the least. Their relative activities to that of 3E22NP were individually calculated. Estrogenic equivalent concentrations of the three technical mixtures were predictively evaluated. The ratio of the EEC to the conventional concentration, total mass percent portions of the 13 isomers in technical mixtures were 0.208 for TCI, 0.206 for Aldrich and 0.205 for Fluka. The predicted estrogenic activity of measured concentration of para-NP in technical mixtures was approximately 5-fold greater than the measured estrogen agonist activity.

Concentrations of polychlorinated biphenyls (PCBs) in beached resin pellets were examined to reveal variability between individual particles and differences among beaches. Fifty-five resin pellets from a beach in Tokyo were individually analyzed for PCBs, and showed concentrations ranging from <28 to 2,300 ng/g. This indicates that concentrations are highly variable between particles. Among several characters, discoloration (e.g., yellowing) had a positive relationship with PCB concentration: discolored pellets contained more PCBs than others on most of the beaches sampled. Given the color-selective ingestion of food by some organisms, this may be ecotoxicologically important. Measurements of samples from 47 beaches in Japan showed regional differences in PCB concentrations in resin pellets consistent with those in mussels. Sporadic high concentrations of PCBs were also found in pellets from remote islands, suggesting that resin pellets could be the dominant route of exposure to the contaminants at remote sites. The similarity of PCB concentrations between resin pellets and mussels suggests a potential use of resin pellets to monitor pollution in seawater.

A comprehensive analytical method of endocrine disrupters (i.e., alkylphenols, phthalic acid esters, bisphenol A, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, DDTs) in environmental samples was developed. The method employs Soxhlet-extraction with dichloromethane and two-step-silica-gel and activated-charcoal column chromatography which provides eleven fractions, followed by determination on capillary GC equipped with MSD or ECD. The present method was applied to Tokyo Bay sediments. Most of the target compounds were identified and quantified clearly demonstrating the applicability to various environmental samples. Their concentrations are as follows: 4-t-octylphenol: 10.0 ng/g; 4-t-nonylphenol: 184 ng/g; benzyl n-butyl phthalate: 6.12 ng/g; dicyclohexyl phthalate: 2.56 ng/g; bisphenol A: 6.58 ng/g; benz[a]anthracene: 58.1 ng/g; benzo[a]pyrene: 93.7 ng/g; IUPAC#77 coplanar PCB: 0.82 ng/g; DDT: 0.42 ng/g; DDD: 1.00 ng/g; DDE: 1.37 ng/g. This method provides a powerful analytical tool to investigate a wide range of endocrine disrupters in samples of limited quantity.

A comprehensive anal. method of endocrine disruptors (i.e., alkylphenols, phthalic acid esters, bisphenol A, polycyclic arom. hydrocarbons, polychlorinated biphenyls, DDTs) in environmental samples was developed. The method employs Soxhlet-extn. with dichloromethane and two-step-silica-gel and activated-charcoal column chromatog., which provides eleven fractions, followed by detn. on capillary GC equipped with MSD or ECD. The present method was applied to Tokyo Bay sediments. Most of the target compds. were identified and quantified clearly, demonstrating the applicability of the method to environmental samples. Their concns. are as follows: 4-tert.-octylphenol 10.0 ng/g; 4-tert.-nonylphenol 184 ng/g; benzyl Bu phthalate: 6.12 ng/g; dicyclohexyl phthalate: 2.56 ng/g; bisphenol A: 6.58 ng/g; benz[a]anthracene: 58.1 ng/g; benzo[a]pyrene: 93.7 ng/g; IUPAC#77 coplanar PCB: 0.82 ng/g; DDT: 0.42 ng/g; DDD: 1.00 ng/g; DDE: 1.37 ng/g. This method provides a powerful anal. tool to investigate a wide range of endocrine disruptors in samples of limited quantity.