Akihiro Iijima

Concentrations, enrichment and predominant sources of Sb and other trace elements in size classified airborne particulate matter collected in Tokyo from 1995 to 2004

APM was collected and trace elements existing in the particles were monitored since May 1995 in this study. APM sample was collected separately by size (d < 2 microm, 2-11 microm and >11 microm) on the roof of the university building (45 m above ground) in the campus of Faculty of Science and Engineering, Chuo University, Tokyo, Japan, using an Anderson low volume air sampler. The collected sample was digested by HNO3, H2O2 and HF using a microwave oven, and major elements (Na, Mg, Al, K, Ca and Fe) were measured by ICP-AES, and trace elements (Li, Be, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Sb, Ba and Pb) were measured by ICP-MS. It was observed that the APM concentration was higher between the winter and the spring, compared to during the summer. The enrichment factor was calculated for each element in each set of APM (d < 2 microm, 2-11 microm and >11 microm). Seasonal trends of enrichment factors were examined, and the elements were classified into 3 groups according to the common seasonal behavior. It is likely that the elements in the same group have common origins. Toxic pollutant elements (Sb, Se, Cd, Pb and As) were found in small particles with d of <2 microm in concentrated levels. Antimony (Sb) had the highest enrichment factor, and the results suggested that Sb level in APM was extremely high. The origins of Sb were sought, and wastes from plastic incineration and brake pad wears of automobiles were suspected. Each set of APM (d < 2 microm, 2-11 microm and >11 microm) was classified by the shape, and the shape-dependent constituents of a single APM particle were quantitatively measured by SEM-EDX. High concentration of Sb was found in APM <2 microm and square particles. Particles less than 2 microm and square shaped particles were major particles produced by actual car braking experiments. From these experimental results it was concluded that the source of Sb in squared APM <2 microm is considered to be from brake pad wear.

Clarification of the predominant emission sources of antimony in airborne particulate matter and estimation of their effects on the atmosphere in Japan

Environmental context. The remarkable enrichment of potentially toxic antimony (Sb) in inhalable airborne particulate matter has become of great environmental concern among recent air pollution issues. The present study clarifies the predominant sources of Sb by focusing on the similarities in elemental composition, particle size distributions, and microscopic images found in ambient airborne particles and several potential sources. We identify automotive brake abrasion dust and fly ash emitted from waste incineration as dominant sources of atmospheric Sb in Japan. These results will contribute towards an in-depth understanding of the cycles and fates of Sb in the environment. Abstract. By focusing on the similarities in elemental composition, particle size distributions of elemental concentrations, and microscopic images between ambient airborne particulate matter (APM) and several potential sources, we discuss the predominant sources of antimony (Sb) in APM in Japan. The distribution of Sb concentration in size-classified ambient APM showed a characteristic bimodal profile in which peaks were found in coarse (3.6–5.2 μm) and fine (0.5–0.7 μm) fractions. Elemental ratios, particle sizes, and microscopic images observed in the coarse APM fractions were found to be in good agreement with those of brake abrasion dust. However, in the fine APM fractions, fly ash originating from waste incineration was identified as the most probable source of Sb. Chemical mass balance analysis was performed to determine the effects of the emission sources of Sb, and it was revealed that brake abrasion dust and waste fly ash were the dominant sources of Sb in the coarser and the finer fractions of APM, respectively. The present study provides important clues to understanding the cycles and fates of Sb in the environment.

Concentration distributions of dissolved Sb(III) and Sb(V) species in size-classified inhalable airborne particulate matter

In order to obtain more accurate assessments of global contamination by potentially toxic antimony (Sb) and the toxicological effects of Sb on ecosystems, speciation analysis of inorganic Sb species in size-classified airborne particulate matter (APM) was performed. Thirteen fractions of size-classified APM (with aerodynamic diameters: Dp 11 μm) were collected on a filter by using a multistage cascade impactor sampler. Speciation analysis of inorganic Sb(III) and Sb(V) was performed by using HPLC-ICP-MS. Portions of sample-loaded filters were sonicated with 30 mmol l−1 citric acid under purified N2 in order to avoid the oxidation of Sb(III) to Sb(V) during the extraction process. Sb(III) and Sb(V) were separated on a PRP-X100 anion exchange column using a mixture of 10 mmol l−1 EDTA and 1 mmol l−1 phthalic acid (pH 4.5) as a mobile phase, and they were subsequently detected by ICP-MS. The size distributions of the total Sb concentration exhibit a bimodal profile in which peaks corresponded to fine (0.50–0.70 μm) and coarse (3.6–5.2 μm) fractions. The speciation analysis demonstrated for the first time that Sb(III), which is the more toxic form, is dominated by coarse fractions whereas Sb(V) is distributed in both the fine and coarse fractions. The presented high-resolution size distributions of inorganic Sb species will provide helpful information in discussing both health risks by inhalation exposure to Sb and the extent of the effects of emission sources by atmospheric circulation.

Relationships between cellular events and signaling pathways in various pesticide-affected neural cells

Various pesticides are considered hazardous to human health. Of particular concern are potential problems of neurotoxicity associated with their use. Cellular toxicity may manifest as a variety of biological events, such as carcinogenesis (mutagenesis) and/or cell death. Recent reports indicate that signaling pathways regulate these cellular events. Thus, the toxicity of pesticides in cells may involve modulation of signaling pathways. In this review, we mainly focus on relationships between cellular events and signaling pathways in various pesticide-affected neural cells. Our data and those of related studies suggest that these pesticides affect both the viability and various signaling pathways of neural cells.