Do we need to examine the quantitative data obtained from toxicity studies for both normality and homogeneity of variance?

Most of the statistical techniques used to evaluate the data obtained from toxicity studies are based on the assumption that the data show a normal distribution and homogeneity of variance. Literature review on toxicity studies on laboratory animals reveals that in most of the cases homogeneity of variance alone is examined for the data obtained from these studies. But the data that show homogeneity of variance need not always show a normal distribution. In fact, most of the data derived from toxicity studies, including hematological and biochemical parameters show a non-normal distribution. On examining normality of data obtained from various toxicity studies using different normality tests, we observed that Shapiro-Wilk test is more appropriate than Kolmogorov-Smimov test, Lilliefors test, the normal probability paper analysis and Chi square test. But there are situations, especially in the long-term toxicity studies, where normality is not shown by one or more than one of the dosage groups. In this situation, we propose that the data maybe analyzed using Dunnett multiple comparison test after excluding the data of the groups that do not show normality However, the biological relevance of the excluded data has to be carefully scrutinized. We also observed that the tendency of the data to show a normal distribution seems to be related to the age of the animals. Present paper describes various tests commonly used to test normality and their power, and also emphasizes the need of subjecting the data obtained from toxicity studies to both normality and homogeneity tests. A flow chart suggesting the statistical techniques that maybe used for both the types of data showing a normal or non-normal distribution is also proposed.     

Control of Mercury Emissions from a Municipal Solid Waste Incinerator in Japan

Abstract

The control of Hg emissions from a municipal solid waste incinerator (MSWI) is very important, because more than 78% of municipal solid waste (MSW) is incinerated. The Hg content of coal used in utility boilers is relatively low in Japan. In this study, recent trends in the Hg content of MSW in Japan and activated carbon (AC) injection as a control technology of Hg emission from an MSWI are discussed. The effect of AC injection on Hg removal from flue gas in an MSWI was investigated by pilot-scale experiments using a bag filter (BF). The injection of AC increases the Hg reduction ratio by 20–30% compared with cases without AC injection. The Hg reduction ratio increases as the flue gas temperature decreases. The Hg reduction ratio is closely related to the inlet Hg concentration and was expressed with a Langmuir-type adsorption isotherm.     

Emissions of polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs from heavy-duty diesel vehicles with DPF and SCR

In total, 24 polycyclic aromatic hydrocarbons (PAHs) in both gas and particle phases and 35 nitro-PAHs in particle phase were analyzed in the exhaust from heavy-duty diesel vehicles equipped with after-treatment for particulate matter (PM) and NO_X control. The test vehicles were carried out using a chassis dynamometer under highway cruise, transient Urban Dynamometer Driving Schedule (UDDS), and idle operation. The after-treatment efficiently abated more than 90% of the total PAHs. Indeed, the particle-bound PAHs were reduced by >99%, and the gaseous PAHs were removed at various extents depending on the type of after-treatment and the test cycles. The PAHs in gas phase dominated the total PAH (gas + particle phases) emissions for all the test vehicles and for all cycles; that is, 99% of the two-ring and 98% of the three-ring and 97% of the four-ring and 95% of the carcinogenic PAHs were in the gas-phase after a diesel particle filter (DPF) and not bound to the very small amount of particulate matter left after a DPF. Consequently, an evaluation of the toxicity of DPF exhaust must include this volatile fraction and cannot be based on the particle fraction only. The selective catalytic reduction (SCR) did not appear to promote nitration of the PAHs in general, although there might be some selective nitration of phenanthrene. Importantly the after-treatmtent reduced the equivalent B[a]P (B[a]Peq) emissions by >95%, suggesting a substantial health benefit.

Implications: This study demonstrated that after-treatments, including diesel particulate filters (DPF), diesel oxidation catalysts (DOC), and selective catalytic reduction (SCR), significantly reduce the emissions of PAHs from heavy-duty diesel engines. The gas-phase PAHs dominate the total PAH (gas + particle phases) emissions from heavy-duty diesel vehicles retrofitted with various DPFs and not bound to the very small amount of particulate matter left after a DPF. Consequently, an evaluation of the toxicity of DPF exhaust must also include this volatile fraction and cannot be based on the particle fraction only.

Supplemental Materials: Supplemental materials are available for this paper. Go to the publisher's online edition of the Journal of the Air & Waste Management Association.     

Demonstration study of high temperature melting for asbestos-containing waste (ACW)

The service life of many buildings and houses built using asbestos-containing materials is coming to an end and their demolition will lead to a great deal of asbestos-containing waste (ACW). Conventionally, the disposal of such waste is conducted by isolation under controlled landfill procedures; however problems with this method exist, such as the risk at the time of re-utilization of landfill sites and the depletion of lands to be reclaimed. Melting treatment is a promising technology that could be used to solve these problems; a thermal process involving temperatures exceeding the melting points of asbestos, it transforms them into non-hazardous minerals. This technology may be applicable not only for friable ACW but also for nonfriable ACW. We performed a demonstration test of melting treatment of nonfriable ACW using a gasification and melting furnace of the shaft furnace type, which is a typical method for high temperature melting. Detailed observation using transmission electron microscopy as well as general analyses verified that the same level of asbestos remained in the slag obtained by high temperature melting as that of the background soil. In addition, the asbestos concentration in the exhaust gas and the dust from the facility were at sufficiently low levels, and it was thus verified that the asbestos concentration in the atmosphere in the vicinity of the facility during the melting treatment was comparable to that of Japan’s background level reported by the Ministry of the Environment in 2007.     

Total OH reactivity and VOC analyses for gasoline vehicular exhaust with a chassis dynamometer

Total OH reactivity for the exhaust gas of gasoline vehicles was measured for the first time under nine different driving conditions with a chassis dynamometer at the National Institute for Environmental Studies (NIES). Along with the total OH reactivity measurements, analysis of trace species such as CH₄, CO, NO, NO₂, and 56 kinds of volatile organic compounds (VOCs), including two aldehydes, was carried out. The ratio of alkanes to alkenes in the exhaust gas turned out to depend on the condition of the driving cycles. There were a considerable number of unidentified peaks obtained during GC analysis. About 15–30% of the total carbon was unidentified species. The chemical compositions of vehicular exhaust were found to depend on the temperature of the engine or catalysts. The contribution of OH reactivity to the species obtained depended on the temperature condition for the engine. The calculated total OH reactivity for VOCs was compared with ozone formation potential (OFP) and it turned out that there are in good correlation, while the correlation for “Cold” start deviates from that for “Hot” start. The measured and calculated OH reactivities were compared with each other. For all driving cycles, the calculated OH reactivity was confirmed to be an underestimation, implying the existence of unknown species in the exhaust gas. The percentage contribution of OH reactivity to the unknown species during “Cold” start was about 17.5%, which was almost the same as that for “Hot” start at 17.0%. However, the absolute value of OH reactivity for “Cold” start was about ten times higher than that for “Hot” start.     

Nitrate facilitates cadmium uptake, transport and accumulation in the hyperaccumulator Sedum plumbizincicola

The aims of this study are to investigate whether and how the nitrogen form (nitrate (NO₃ ^–) versus ammonium (NH₄ ⁺)) influences cadmium (Cd) uptake and translocation and subsequent Cd phytoextraction by the hyperaccumulator species Sedum plumbizincicola. Plants were grown hydroponically with N supplied as either NO₃ ^– or NH₄ ⁺. Short-term (36 h) Cd uptake and translocation were determined innovatively and quantitatively using a positron-emitting ¹⁰⁷Cd tracer and positron-emitting tracer imaging system. The results show that the rates of Cd uptake by roots and transport to the shoots in the NO₃ ^– treatment were more rapid than in the NH₄ ⁺ treatment. After uptake for 36 h, 5.6 (0.056 μM) and 29.0 % (0.290 μM) of total Cd in the solution was non-absorbable in the NO₃ ^– and NH₄ ⁺ treatments, respectively. The local velocity of Cd transport was approximately 1.5-fold higher in roots (3.30 cm h^?1) and 3.7-fold higher in shoots (10.10 cm h^?1) of NO₃ ^–- than NH₄ ⁺-fed plants. Autoradiographic analysis of ¹⁰⁹Cd reveals that NO₃ ^– nutrition enhanced Cd transportation from the main stem to branches and young leaves. Moreover, NO₃ ^– treatment increased Cd, Ca and K concentrations but inhibited Fe and P in the xylem sap. In a 21-day hydroponic culture, shoot biomass and Cd concentration were 1.51 and 2.63 times higher in NO₃ ^–- than in NH₄ ⁺-fed plants. We conclude that compared with NH₄ ⁺, NO₃ ^– promoted the major steps in the transport route followed by Cd from solution to shoots in S. plumbizincicola, namely its uptake by roots, xylem loading, root-to-shoot translocation in the xylem and uploading to the leaves. S. plumbizincicola prefers NO₃ ^– nutrition to NH₄ ⁺ for Cd phytoextraction.     

Temporal trends and sources of PCDD/Fs, pentachlorophenol and chlornitrofen in paddy field soils along the Yoneshiro River basin, Japan

In order to understand the long-term behaviors of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), pentachlorophenol (PCP), and 2,4,6-trichlorophenyl-4′-nitrophenyl ether (chlornitrofen, CNP) in paddy soil, we measured their concentrations in paddy soil samples collected in 1982 and 1984 (1980s) and in 2000 and 2002 (2000s) from the Yoneshiro River basin, Japan. The concentrations of PCP and CNP decreased from the 1980s to the 2000s, whereas the concentrations of PCDD/Fs and their toxic equivalency (WHO2006-TEQ) remained. The major sources of PCDD/Fs in the paddy soil samples were attributed to impurities in PCP and CNP as a result of comparisons of homologue and congener profiles and principal component analysis. Based on the results of comparison of total input and remaining amount, it is estimated that more than 99% of PCP and CNP applied to the paddy fields had disappeared, whereas most of the applied PCDD/Fs and TEQ remained.     

Long-term Trends in Surface Water Quality of Five Lakes in Japan

Since 1983, the Ministry of the Environment of Japan has conducted nation-wide acid deposition surveys. To investigate the effects of acid deposition on surface water, we used the nonparametric Mann–Kendall test to find temporal trends in pH, alkalinity, and electrical conductivity (EC) in more than 10 years of data collected from five lakes and their catchments (Lake Kuttara: northernmost; Lake Kamakita: near Tokyo; Lake Ijira: central; Lake Banryu: western; and Lake Unagiike: southernmost). The pH of Lake Ijira water has declined slightly since the mid-1990s, corresponding with the downward trends seen in the pH and alkalinity of the river water flowing into the lake. There were significant upward trends in the EC of both the lake and stream water; the same trends were also found for concentrations. These trends show evidence of acidification due to atmospheric deposition, and this is the first such finding in Japan based on significant long-term trends. Lake Ijira is located about 40 km north of the Chukyo industrial area near Nagoya. The annual depositions of H⁺, nss-, and in Lake Ijira were among the highest of all deposition monitoring sites, suggesting that this is the main cause of the significant acidification observed in Lake Ijira. No significant trends suggesting acidification were observed in any of the other lake catchments in spite of the significant upward trends in EC. Upward trends in pH and alkalinity at Lake Banryu and upward trends in alkalinity at Lake Kamakita were detected, but no change in pH or alkalinity at Lake Kuttara and Lake Unagiike was observed.     

Aggregation and Aggregate Strength of Microscale Plastic Particles in the Presence of Natural Organic Matter: Effects of Ionic Valence

Journal of Polymers and the Environment - Considering the recent plastic loads in water bodies we studied the aggregation, charging, and aggregate strength of polyethylene microsphere (PEM)...     

Source-specific sewage pollution detection in urban river waters using pharmaceuticals and personal care products as molecular indicators

Environmental Science and Pollution Research - Source-specific elucidation of domestic sewage pollution caused by various effluent sources in an urban river water, as conducted for this study,...