Effect of Mesioangular Impaction of the Mandibular Third Molars on the Adjacent Mandibular Second Molars: An Imaging Study.

OBJECTIVE: To investigate the effect of mesioangular impaction of the mandibular third molars on distal caries and distal bone loss (DBL) in the adjacent mandibular second molars to provide a basis for prophylactic impacted third molar extraction. METHODS: We retrospectively analyzed panoramic radiographs of 736 patients with mesioangularly impacted mandibular third molars at the Department of Stomatology, Shanghai Fifth People's Hospital. The chi-square test, the Kruskal-Wallis test, and logistic regression were performed to analyze the relationship of patient age, sex, mesial inclination angle, distal caries, and DBL in the mandibular second molars. RESULTS: Patient aged over 30 years and a mesial inclination angle > 30° were risk factors for distal caries in the mandibular second molars (p < 0.05). Patients aged over 20 years and a mesial inclination angle of 60°-90° were risk factors for DBL (p < 0.05). CONCLUSION: In patients with mesioangularly impacted mandibular third molars, age and the mesial inclination angle were positively correlated with the severity of distal caries and DBL in the adjacent mandibular second molars. These findings could guide dental practitioners to prevent complications of the adjacent molars during early prophylactic extraction of the mandibular third molars with mesioangular inclination.

Source apportionment and health risk assessment of trace metals in surface soils of Beijing metropolitan, China.

Understanding the exposure risks of trace metals in contamination soils and apportioning their sources are the basic preconditions for soil pollution prevention and control. In this study, a detailed investigation was conducted to assess the health risks of trace metals in surface soils of Beijing which is one of the most populated cities in the world and to apportion their potential sources. The data set of metals for 12 elements in 240 soil samples was collected. Pollution index and enrichment factor were used to identify the general contamination characteristic of soil metals. The probabilistic risk model was employed for health risk assessment, and a chemometrics technique, multivariate curve resolution-weighted alternating least squares (MCR-WALS), was applied to apportion sources. Results suggested that the soils in Beijing metropolitan region were contaminated by Hg, Cd, Cu, As, and Pb in varying degree, lying in the moderate pollution level. As a whole, the health risks posed by soil metals were acceptable or close to tolerable. Comparatively speaking, children and adult females were the relatively vulnerable populations for the non-carcinogenic and carcinogenic risks, respectively. Atmospheric deposition, fertilizers and agrochemicals, and natural source were apportioned as the potential sources determining the contents of trace metals in soils of Beijing area with contributions of 15.5%-16.4%, 5.9%-7.7% and 76.0%-78.6%, respectively.

Environmental distribution and associated human health risk due to trace elements and organic compounds in soil in Jiangxi province, China.

The government of China launched its first national soil quality and pollution survey (NSQPS) during April 2006 to December 2013. Data gathered in several earlier soil surveys were rarely used to understand the status of pollution. In this study, the dataset collected at the provincial level was analyzed for the first time. Concentrations, distribution, diversity, and human health risks of trace elements (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Se, V and Zn) and organic pollutants (benzene hexachloride (BHCs), dichlorodiphenyltrichloroethanes (DDTs), phthalic acid esters (PAEs), polycyclic aromatic hydrocarbon (PAHs), polychlorinated biphenyls (PCBs), and petroleum hydrocarbons (PHCs)) in surface soil samples collected across Jiangxi province,China were presented. The results showed that, the proportion of contaminants with concentrations higher than their corresponding regulatory reference value ranged from 0.12% to 17%. It is worth note that, the local residents are exposed to moderate non-carcinogenic and carcinogenic risks at some sites. The comprehensive analysis of soil pollutants provide baseline information for establishing a long-term soil environmental monitoring program in Jiangxi province, China.

Heavy metal pollution and ecological risk assessment of the paddy soils near a zinc-lead mining area in Hunan.

Soil pollution by Cd, Hg, As, Pb, Cr, Cu, and Zn was characterized in the area of the mining and smelting of metal ores at Guiyang, northeast of Hunan Province. A total of 150 topsoil (0-20 cm) samples were collected in May 2012 with a nominal density of one sample per 4 km(2). High concentrations of heavy metals especially, Cd, Zn, and Pb were found in many of the samples taken from surrounding paddy soil, indicating a certain extent of spreading of heavy metal pollution. Sequential extraction technique and risk assessment code (RAC) were used to study the mobility of chemical forms of heavy metals in the soils and their ecological risk. The results reveal that Cd represents a high ecological risk due to its highest percentage of the exchangeable and carbonate fractions. The metals of Zn and Cu pose a medium risk, and the rest of the metals represent a low environmental risk. The range of the potential ecological risk of soil calculated by risk index (RI) was 123.5~2791.2 and revealed a considerable-high ecological risk in study area especially in the neighboring and surrounding the mining activities area. Additionally, cluster analyses suggested that metals such as Pb, As, Hg, Zn, and Cd could be from the same sources probably related to the acidic drainage and wind transport of dust. Cluster analysis also clearly distinguishes the samples with similar characteristics according to their spatial distribution. The results could be used during the ecological risk screening stage, in conjunction with total concentrations and metal fractionation values to better estimate ecological risk.

Contamination features and health risk of soil heavy metals in China.

China faces a big challenge of environmental deterioration amid its rapid economic development. To comprehensively identify the contamination characteristics of heavy metals in Chinese soils on a national scale, data set of the first national soil pollution survey was employed to evaluate the pollution levels using several pollution indicators (pollution index, geoaccumulation index and enrichment factor) and to quantify their exposure risks posed to human health with the risk assessment model recommended by the US Environmental Protection Agency. The results showed that, due to the drastically increased industrial operations and fast urban expansion, Chinese soils were contaminated by heavy metals in varying degrees. As a whole, the exposure risk levels of soil metals in China were tolerable or close to acceptable. Comparatively speaking, children and adult females were the relatively vulnerable populations for the non-carcinogenic and carcinogenic risks, respectively. Cadmium and mercury have been identified as the priority control metals due to their higher concentrations in soils or higher health risks posed to the public, as well as, arsenic, lead, chromium and nickel. Spatial distribution pattern analysis implied that the soil metal pollutions in southern provinces of China were relatively higher than that in other provinces, which would be related to the higher geochemical background in southwest regions and the increasing human activities in southeast areas. Meanwhile, it should be noticed that Beijing, the capital of China, also has been labeled as the priority control province for its higher mercury concentration. These results will provide basic information for the improvement of soil environment management and heavy metal pollution prevention and control in China.

Evaluation of soil contamination indices in a mining area of Jiangxi, China.

There is currently a wide variety of methods used to evaluate soil contamination. We present a discussion of the advantages and limitations of different soil contamination assessment methods. In this study, we analyzed seven trace elements (As, Cd, Cr, Cu, Hg, Pb, and Zn) that are indicators of soil contamination in Dexing, a city in China that is famous for its vast nonferrous mineral resources in China, using enrichment factor (EF), geoaccumulation index (Igeo), pollution index (PI), and principal component analysis (PCA). The three contamination indices and PCA were then mapped to understand the status and trends of soil contamination in this region. The entire study area is strongly enriched in Cd, Cu, Pb, and Zn, especially in areas near mine sites. As and Hg were also present in high concentrations in urban areas. Results indicated that Cr in this area originated from both anthropogenic and natural sources. PCA combined with Geographic Information System (GIS) was successfully used to discriminate between natural and anthropogenic trace metals.

[Soil heavy metal cadmium standard limit and range of background value research].

With the rapid development of industrial and agricultural production in China, problems such as excessive soil pollutants worsen year by year, and soil cadmium pollution resulting from the emergence of "cadmium rice" and other food security incidents occur frequently. It causes the extensive concern of society on soil cadmium environmental standards. A soil environmental standard is the foundation for the evaluation of soil environmental quality. The maximum allowable value of cadmium that affects plant and animal and human health is regarded as the basis value all over the world; however, the certification methods and the goals of standard application are different, thus the standard limit has a great difference. Through the research on domestic and foreign soil cadmium standard limits and the soil cadmium background values in China, the soil cadmium background content range values of the provinces and of some types of soil are given. We report the outstanding problems existing in China's current environmental quality standard of soil cadmium. It is proposed that the soil environmental quality standard should allow the coexistence of gradient of soil cadmium standard limit, effective state and total standard limit, and anthropogenic pollution and background values exceeding the standard should be strictly distinguished.

Soil and soil environmental quality monitoring in China: a review.

Over the past few decades, numerous concerns have been raised in China over the issue of environmental sustainability. Various soil survey and monitoring programs have been carried out in China to study soil quality, and to provide a scientific basis for environment policy making. This paper provides an overview of past and current soil quality surveys and monitoring activities in China. This paper includes a summary of concerns over background concentrations of elements in soil, and soil environmental standards and guidelines in China. Levels of pollution in urban soil, agricultural soil, and soil in mining and smelting areas were compared using the concentrations and pollution indexes. In addition to soil surveys, soil monitoring is essential to study the data and to examine the effects of contaminants in soils. However, the current soil quality monitoring system was insufficient to accurately determine the soil quality status of soils across China. For accurate soil monitoring in China, it will be necessary to set up routine monitoring systems at various scales (national, provincial, and local scales), taking into consideration monitoring indicators and quality assurance. This is currently an important priority for the environmental protection administration of China.

Enhancement of pyrene removed from contaminated soils by Bidens maximowicziana.

The research utilized Bidens maximowicziana along with pyrene-degrading bacteria to evaluate their potential in cleaning up pyrene contamination. The removal of pyrene from the planted soil was obviously higher than that from the unplanted soils. After 50 d of B. maximowicziana growth, the average removal ratio of pyrene in planted soil was 79%, which was 28% higher than that of pyrene in unplanted soil. In contrast to other plants, both roots and shoots of B. maximowicziana could accumulate a large amount of pyrene from the soil and pyrene uptake increased with the soil pyrene concentration. Through analysis of pathways of pyrene removal, this enhanced removal of pyrene by plant-microbial association might be mainly the result of B. maximowicziana-promoted microbial degradation. Both the catalase and polyphenol oxidase activities in soil were higher in planted soil than those in unplanted soil. And the bacteria populations in soil, especially in rhizosphere, were also inspired by the growth of B. maximowicziana. These could be explained by the rhizosphere effect. Therefore, bio-removal of pyrene in the contaminated soils was feasible using B. maximowicziana.

EDTA-enhanced phytoremediation of lead contaminated soil by Bidens maximowicziana.

Phytoremediation is a potential cleanup technology for the removal of heavy metals from contaminated soils. Bidens maximowicziana is a new Pb hyperaccumulator, which not only has remarkable tolerance to Pb but also extraordinary accumulation capacity for Pb. The maximum Pb concentration was 1509.3 mg/kg in roots and 2164.7 mg/kg in overground tissues. The Pb distribution order in the B. maximowicziana was: leaf > stem > root. The effect of amendments on phytoremediation was also studied. The mobility of soil Pb and the Pb concentrations in plants were both increased by EDTA application. Compared with CK (control check), EDTA application promoted translocation of Pb to overground parts of the plant. The Pb concentrations in overground parts of plants was increased from 24.23-680.56 mg/kg to 29.07-1905.57 mg/kg. This research demonstrated that B. maximowicziana appeared to be suitable for phytoremediation of Pb contaminated soil, especially, combination with EDTA.

Isolation and characterization of gasoline-degrading bacteria from gas station leaking-contaminated soils.

The effects of culture conditions in vitro and biosurfactant detection were studied on bacterial strains capable of degrading gasoline from contaminated soils near gas station. The main results were summarized as follows. Three bacteria (strains Q 10, Q14 and Q18) that were considered as efficiently degrading strains were isolated and identified as Pseudomonas sp., Flavobacterium sp. and Rhodococcus sp., respectively. The optimal growth conditions of three bacteria including pH, temperature and the concentration of gasoline were similar. The reduction in surface tension was observed with all the three bacteria, indicating the production of biosurfactant compounds. The value of surface tension reduced by the three strains Q10, Q14 and Q18 was 32.6 mN x m, 12.4 mNx m and 21.9 mN x m, respectively. Strain Q10 could be considered as a potential biosurfactant producer. Gasoline, diesel oil, benzene, toluene, ethylbenzene and xylene (BTEX) could easily be degraded by the three isolates. The consortium was more effective than the individual cultures in degrading added gasoline, diesel oil, and BTEX. These results indicate that these strains have great potential for in situ remediation of soils contaminated by gas station leaking.

[Bidens maximowicziana's adsorption ability and remediation potential to lead in soils].

Bidens maximowicziana's adsorption ability and remediation potential to lead were studied. The results show: (1) The Bidens maximowicziana has a strong adsorption to lead, the concentration of lead in plants increased linearly with the increase of lead concentration in soil. Then maximum concentration was 1509.3 mg x kg(-1) in roots and 2164.7 mg x kg(-1) in shoots when lead concentration in soil was 2000 mg x L(-1); (2) The lead concentration distribution order in the Bidens maximorwicziana is: leaf>stem>root>seed, which indicate that Bidens maximowicziana has a strong ability to transfer lead; (3) Uptaking ability differes in different vegetal periods. Maximum lead uptaking rate occured in the period of blooming for 40-60 days, in which daily uptake capacity was 15.81 mg x (kg x d)(-1) in roots and 19.83 mg x (kg x d)(-1) in shoots respectively. It can be concluded that Bidens maximowicziana appeares to be a moderate Pb accumulator making it suitable for phytoremediation of Pb contaminated soil.