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Estimation of the soil hazardous concentration of methylparaben using a species sensitivity approach
Kim, Dokyung,Cui, Rongxue,Moon, Jongmin,Kwak, Jin Il,Kim, Shin Woong,Kim, Dasom,An, Youn-Joo Elsevier 2018 Environmental pollution Vol.242 No.1
<P><B>Abstract</B></P> <P>Methylparaben, which is known to be an endocrine-disrupting chemical, is added to various personal care products, including cosmetics, and is also used as a food preservative and in pharmaceuticals. However, information on the toxicity of methylparaben in soil ecosystems is limited. Furthermore, unlike other substances such as metals and pesticides, there is no regulation of levels or safe concentrations of methylparaben in soil ecosystems. Therefore, the aims of this study were to evaluate the toxicity of methylparaben on soil species and to derive hazardous concentration (HC) values with respect soil ecosystem protection. We conducted acute bioassays on eight species within six taxonomic groups and chronic bioassays on five species within four taxonomic groups. On the basis of the results obtained, we derived an acute HC<SUB>5</SUB> value of 44 mg/kg soil and a corresponding chronic value of 27 mg/kg soil for methylparaben using species sensitivity distribution methodology following Australian and New Zealand guidelines. Given that there has been no proposed standard value for methylparaben in soil in any country, it was not possible to compare the HC values calculated in this study with regulation standard levels. Nevertheless, to our knowledge, this study is first to assess the toxicity of methylparaben against soil-inhabiting species and to estimate acute and chronic HCs for soil fauna and flora. The results of this study will provide valuable fundamental data for the establishment of acceptable levels of methylparaben in soil.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ecotoxicology assessment of methylparaben were performed using soil species. </LI> <LI> We derived soil methylparaben hazardous concentrations based on species sensitivity. </LI> <LI> Our results can be used to establish safe baseline concentrations for methylparaben. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kim, Dokyung,Ha, Jung-Hong,Jin, Myoung-Uk,Kim, Young-Kyung,Kim, Sung Kyo The Korean Academy of Conservative Dentistry 2016 Restorative Dentistry & Endodontics Vol.41 No.3
Objectives: The purpose of this study was to evaluate the proximity of the mandibular molar apex to the buccal bone surface in order to provide anatomic information for apical surgery. Materials and Methods: Cone-beam computed tomography (CBCT) images of 127 mandibular first molars and 153 mandibular second molars were analyzed from 160 patients' records. The distance was measured from the buccal bone surface to the root apex and the apical 3.0 mm on the cross-sectional view of CBCT. Results: The second molar apex and apical 3 mm were located significantly deeper relative to the buccal bone surface compared with the first molar (p < 0.01). For the mandibular second molars, the distance from the buccal bone surface to the root apex was significantly shorter in patients over 70 years of age (p < 0.05). Furthermore, this distance was significantly shorter when the first molar was missing compared to nonmissing cases (p < 0.05). For the mandibular first molars, the distance to the distal root apex of one distal-rooted tooth was significantly greater than the distance to the disto-buccal root apex (p < 0.01). In mandibular second molar, the distance to the apex of C-shaped roots was significantly greater than the distance to the mesial root apex of non-C-shaped roots (p < 0.01). Conclusions: For apical surgery in mandibular molars, the distance from the buccal bone surface to the apex and apical 3 mm is significantly affected by the location, patient age, an adjacent missing anterior tooth, and root configuration.
Kim, Eun Jin,Lee, Dokyung,Moon, Se Hoon,Lee, Chan Hee,Kim, Sang Jun,Lee, Jae Hyun,Kim, Jae Ouk,Song, Manki,Das, Bhabatosh,Clemens, John D.,Pape, Jean William,Nair, G. Balakrish,Kim, Dong Wook Public Library of Science 2014 PLoS pathogens Vol.10 No.9
<▼1><P>Pandemic <I>V. cholerae</I> strains in the O1 serogroup have 2 biotypes: classical and El Tor. The classical biotype strains of the sixth pandemic, which encode the classical type cholera toxin (CT), have been replaced by El Tor biotype strains of the seventh pandemic. The prototype El Tor strains that produce biotype-specific cholera toxin are being replaced by atypical El Tor variants that harbor classical cholera toxin. Atypical El Tor strains are categorized into 2 groups, Wave 2 and Wave 3 strains, based on genomic variations and the CTX phage that they harbor. Whole-genome analysis of <I>V. cholerae</I> strains in the seventh cholera pandemic has demonstrated gradual changes in the genome of prototype and atypical El Tor strains, indicating that atypical strains arose from the prototype strains by replacing the CTX phages. We examined the molecular mechanisms that effected the emergence of El Tor strains with classical cholera toxin-carrying phage. We isolated an intermediary <I>V. cholerae</I> strain that carried two different CTX phages that encode El Tor and classical cholera toxin, respectively. We show here that the intermediary strain can be converted into various Wave 2 strains and can act as the source of the novel mosaic CTX phages. These results imply that the Wave 2 and Wave 3 strains may have been generated from such intermediary strains in nature. Prototype El Tor strains can become Wave 3 strains by excision of CTX-1 and re-equipping with the new CTX phages. Our data suggest that inter-chromosomal recombination between 2 types of CTX phages is possible when a host bacterial cell is infected by multiple CTX phages. Our study also provides molecular insights into population changes in <I>V. cholerae</I> in the absence of significant changes to the genome but by replacement of the CTX prophage that they harbor.</P></▼1><▼2><P><B>Author Summary</B></P><P>In this report, we suggest a genetic mechanism of how the <I>V. cholerae</I> atypical El Tor variants were generated from classical and prototype El Tor biotype strains. An intermediary strain, containing the CTX-1 and CTX-2 prophages, was identified among the clinical isolates that were collected in 1991, when the atypical strains emerged. This strain can be converted into various Wave 2 atypical El Tor strains by eliminating prototype components, CTX-1 and RS1. Further, new types of the CTX phage genome can be generated from the intermediary strain by inter-chromosomal recombination between CTX phages and recombination between the CTX phage and RS1. These new CTX phages can be transduced into other El Tor strains, transforming them into Wave 3 atypical strains. This is a demonstrated instance of how a single-segment-genome CTX phage re-organizes its genome through recombination between different types of phage, leading to generation of new phage variants and atypical El Tor strains.</P></▼2>
부지특이적 토양생태위해성평가를 위한 생태위해지수 산정기법 비교연구
김도경(Dokyung Kim),곽진일(Jin Il Kwak),최영설(Rongxue Cui),김리아(Lia Kim),이태양(Tae Yang Lee),김해미(Haemi Kim),안윤주(Youn-Joo An) 대한환경공학회 2022 대한환경공학회지 Vol.44 No.11
목적 : 토양환경에 존재하는 오염물질의 위해성은 토양의 특성과 기능, 그리고 환경조건 등에 따라 달라질 수 있으므로 부지특이적 특성을 반영하는 것이 필수적이다. 국제표준안 및 국외 생태위해성평가 지침에서는 자국 실정에 적합한 위해성평가 기법을 통하여 부지특이적 토양생태위해성평가를 수행하도록 제안하고 있다. 그러나 국내의 경우 부지특이적 생태위해성평가 제도 도입 기반이 부족한 실정이므로 국내 실정에 맞는 생태위해성평가 기법이 요구된다. 이에 따라 본 연구에서는 부지특이적 생태위해성을 반영할 수 있는 인자를 스크리닝하여 국내형 생태위해성평가 기법 개발의 방향성을 제안하는 것을 목표로 하였다. 방법 : 기존 문헌에서 제안 및 활용된 생태위해지수를 분석하고 각 인자에 대한 산정 방법을 설명하였다. 조사된 생태위해지수는 화학적 평가, 독성학적 평가, 그리고 통합적 평가를 기반으로 한 인자로 분류되었다. 결과 및 토의 : 화학적 평가 기반 인자의 경우 신속한 오염도 산정이 가능하나 토양특성을 반영하기 어렵고 생태수용체와의 연관성을 나타낼 수 없다는 한계점이 존재한다. 독성학적 평가 기반 인자는 생태수용체에 대한 영향을 바탕으로 위해도를 산정할 수 있으나 현장 내에서 실험이 이루어지지 않기 때문에 대상부지의 환경조건 등을 재현하기 어렵다는 제한점이 있다. 통합적 평가 기반 인자는 화학적 평가, 독성학적 평가와 함께 대상부지에 대한 생태학적 평가를 수행하여 오염도를 정량화하고 생태수용체의 취약성, 부지특이성 등을 반영함으로써 생태위해도를 나타낸다. 결론 : 국내형 부지특이적 생태위해성평가 기법은 현장 토양의 오염도와 함께 생태수용체 및 생태학적 특성 등을 포괄하는 통합적 평가기반 위해지수를 기반으로 마련되어야 한다. Objectives : Since the risk of pollutants in soil environment may vary depending on the characteristics, functions, and environmental conditions of the soil, the site-specific soil ecological risk assessment (SERA) should be conducted to protect soil ecosystem from pollutants. It has been confirmed that each country is conducting SERAs based on site-specific guidelines suitable for their own conditions. However, in Korea, there is a lack of basis for introducing SERA, therefore, the development of techniques for SERA which is suitable for domestic soil conditions is required. Accordingly, this study aimed to propose the direction of domestic guideline for SERA. Methods : This study investigated and analyzed the ecological risk indices for SERA. The factors were classified the ecological risk indices based on chemical, toxicological, and integrated evaluations. Results and Discussion : For the chemical indices, they have limitations that it is difficult to reflect soil characteristics and cannot indicate a relation with ecological receptors, although they can calculate contamination level rapidly. The toxicological indices can calculate the effect of pollutions on ecological receptors. However, there are also limitations that it is difficult to reproduce environmental conditions for target site. While the integrated indices require the ecological assessment along with chemical, toxicological analysis. They are found to quantify complex contaminations with reflecting site-specific characteristics of soils and ecological receptors. Conclusion : The techniques for domestic site-specific SERA should be based on the indices for integrated assessment.
Assessing aquatic toxicity of leachates from shoe sole fragments
Lia Kim(김리아),Dokyung Kim(김도경),Sang A Kim(김상아),Haemi Kim(김해미),Tae-Yang Lee(이태양),Youn-Joo An(안윤주) 환경독성보건학회 2021 한국독성학회 심포지움 및 학술발표회 Vol.2021 No.5
Microplastics generated from the land contribute a high portion of plastic waste, such as shoe sole fragments or tire wear. These particles could be exposed to aquatic environments in all days and leaching some chemicals such as additives, used in the product manufacturing process. This study investigated the toxicity of shoe sole fragments on three aquatic organisms (Chlamydomonas reinhardtii, Daphnia magna, and Danio rerio) using their leachates. The adverse effects on each test species were measured and chemical component analysis in each leachate were conducted. The results of toxicity effects and chemical component were compared and the most relevant chemical were determined using the principal component analysis. In results, the aquatic toxicity was highly related to the chemicals such as benzothiazole, carbon disulfide, and p-xylene, which were detected only in sneakers leachates. These results indicate that the road-originated microplastics could leach some toxic chemicals when exposed to aquatic media, inducing the significant adverse effects on the aquatic organisms. The small-size plastic discharge have a risk of their chemical-leaching property that it would be essential to regulate the chemicals in plastic-production process to prevent from the severity of microplastic toxicity.