On account of the highly volatile property of mercury and its compounds the atmosphere is considered to play an important role in global cycle of mercury. This review summarizes the results so far obtained on the concentration of mercury in air, together with those in various environmental samples pertinent to the atmospheric distribution of mercury.
The background concentration of total mercury in air near the ground surface is estimated to be 2-3 ng/m³.Atmospheric mercury is considered to consist mainly of gaseous mercury. The lower concentrations of totalmercury were reported in the upper regions of the atmosphere and over oceans. Higher concentrations were observed in the urban ambient air.
Mercury is emitted from natural and anthropogenic sources, but it has not been yet clarified which source stronger in emission because of the difficulty in the measurement of the natural source-strength.
The main removal process of atmospheric mercury is the wet deposition. Mercury concentrations in precipitation were reported to be 1-200 ng/l. It was observed that only several percent of total mercury released from a point emission source deposits in its neighboring areas and most parts of the released mercury disperse much more widely.

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The equipment for breeding of animals, composed of ambient and filtered air rooms, was settled at the roadside in Yokohama City where traffic was very heavy. One hundred and sixty male rats (JCL-Wister) were halved and raised in each room for as long as 88 weeks. In order to investigate the effects of air pollution, antibodyforming cells (AFC) in spleen, and cervical and mesenteric lymph nodes, and serum haemagglutination were quantitated after intraperitoneal (i. p.) injection with sheep red blood cells (SRBC), in addition to measurement of body weight and hematological examinations. The results can be summarized as follows:
1) Monthly average of the concentration of air pollutants in the ambient air room and the filtered air room were, respectively, 0.020-0.034 ppm and 0.008-0.014 ppm of nitrogen dioxide, 0.024-0.049 ppm and 0.003-0.014 ppm of nitrogen monoxide, 0.007-0.012 ppm and 0.002-0.005 ppm of sulfur dioxide, and 0.030-0.060mg/m³ and 0.017-0.019 mg/m³ of suspended particulate matter. The former data were coinsided with that monitored independently by Environment Department, Kanagawa Prefecturel Government at the nearest part of the same roadside.
2) Increase of body weight of rats kept in the ambient air room was inhibited significantly at the age of 5 to 8 weeks and 30 to 44 weeks compared with that of control group bred in the filtered air room, although no significant difference between these two groups was observed in the hematological examinations including RBC number, WBC number, haematocrit, hemoglobin concentration, and levels of serum IgG and IgM throughout the period of experiment.
3) Until 26 weeks of breeding, significant difference was not noted in these two groups concerning antibodyproducing ability as measured by AFC number in spleen and other lymphoid organs against i.p. injection of SRBC. After raising for longer period, slight but significant suppression was observed in the ambient air group of rats showing decreased number of AFC in spleen on day 5, and cervical and mesenteric lymph nodes on day 8 and 10 postimmunization at 60 and 88 weeks, respectively. Levels of haemagglutinin in sera did not reflect the difference detected in the preceding experiment.
The present results seem to indicate the suppressive effect of air pollution upon the antibody-producing ability of rats bred for long period even if the concentrations of air pollutants are as low as that observed at a roadside of a busy traffic.

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In our preliminary investigation (J. Japan Soc. Air Pollut., 20, 279-285, 1985), it was considered that the pear leaf damages were caused by the accumulation of iodine which was emitted from a iodine refinery. Therefore, the iodine pollution was examined by the arrangement method of potted pear trees (Pyrus serotina REHDER var. culta REHDER cv. Kosui) at the distances of 0, 0.2, 0.7 and 30 km from the iodine refinery. The appearance of leaf damages and accumulation of iodine in leaves were analyzed.
The leaf damages were observed on the potted pear trees only located in the iodine refinery. The nearer from the iodine refinery, the higher was the iodine concentration of pear leaves. These results showed that the pollution source of iodine was the iodine refinery. The polluted area reached to about 0.7 kilometer from the iodine refinery. It was also found that the iodine of pear leaves was absorbed through the leaf from atmosphere.
The growth of pear shoots was depressed by iodine pollution. The iodine threshold concentration, which included the growth distortion on pear shoots, was estimated to be 6-10 ppm, and that for leaf damages was about 30 ppm in Kosui pear, a sensitive cultivar.

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A cryogenic collection method is developed for routine use in the analysis of atmospheric peroxyacetyl nitrate (PAN) with a gas chromatograph (GC)-electron capture detector (ECD). Six tiubes were tested for a collecting trap by using liquid oxygen as a refrigerant. These tubes were composed of four-Teflon tube [1.0-3.0 mm (i.d.), 30-200 cm (1.)] packed with Teflon beads or Teflon wool or unpacked, a Pyrex glass tube [3mm (i.d.), 30 cm (1.)] packed with Pyrex glass beads, and a open stainless steel tube [0.8 mm (i.d.), 300 cm (1.)] The Teflon tube (3 mm × 30 cm) packed with 0.3 g Teflon beads (‘A’ tube) was found to be most suitable for a collecting trap by reasons of high recovery of PAN, ease of preparation and handling conveniences. The effect of desorption temperature on PAN decomposition in the ‘A’ tube can be ignored in the range of 0× to 70×C.
The break-through volume of the ‘A’ tube for PAN is more than 2.5 liter at the temperature of liquid oxygen temperature, thus the cryogenic collection method connecting to GC-ECD allows the determination of PAN at several tens ppt (parts per trillion, 10^-12 v/v) with sufficient sensivity and adequate precision. PAN in the ‘A’ tube chilled with liquid oxygen is stable beyond forty -eight hours, then, this collection method also allows the air sampling for PAN at the site far from a laboratory. Diurnal variation of atmospheric PAN was measured by GC-ECD with the cryogenic collection method and with the direct injection method at the same place for two days. Any practical difference was not observed between the PAN concentrations by these two method.

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Chronic inhalation of diesel exhaust gas (particulate, 4.9±1.6 mg/m³) to Fisher 344 strain SPF rats, were carried out up to 2 years, and histopathological findings were studied at 1, 3, 6, 12 and 24 months after the start of exposure and after further 6 months observation without exposure.
The prominent change observed in the lungs of whole-exhaust exposed rat was deposition of the inhaled particulates in the alveolar spaces being taken by alveolar macrophages, associated with proliferation of type II alveolar epitheliums on the alveolar wall and of respiratory bronchiolar epitheliums, which extended towards alveolar ducts and neighboring alveoli.
These proliferative foci of the both kinds of epitheliums appeared in the lungs of 6 months exposed rats, increased their extent in accordance with exposure duration and/or age.
Neoplastic change was found in the lungs of 2 year, whole-exhaust exposed rats in 8 of 19 (42.1%), some of which showed malignancy in 5 of 19 (26.3%).
Two types of lung cancer, adenocarcinoma and adenosquamous/squamous carcinoma were seen, probably representing the two different original cells, type II alveolar epithelium and bronchiolar one.
Malignant lymphoma of the spleen with or without leukemia was the major cause of death after 1 year exposure, and significantly higher rate of this pathological condition was observed in the whole-exhaust exposed and filtered-exhaust exposed groups than in the control group. Histologically, two types of the change were noted, lymph folicle replacing type and red-pulp infiltrating one. The latter developed more to leukemia than the former.
Mammary gland adenoma and subcutaneous fibroma developed more in both of the exposed groups than control one and sarcoma was detected only in the whole-exhaust exposed groups. Multi-tumor bearing rats were found in the two exposed groups but not in the control one.
Further studies under various exposure conditions are required in future.

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Concentrations of organic carbon (C_ao) and Elemental carbon (C_ae) in ambient particulate matter were meas-ured over the Tokyo metropolitan area on July 23, 1982. The lowest and the highest concentrations of each carbon were appeared in early morning and midday time, respectively. The every peaks of [C_ao]/[C0], [C_ao]/[CH=CH] and [C_ao]/[C_ae] were appeared in midday time or late afternoon. The half part of C_ao measured in the daytime is estimated to be formed secondarily in the atmosphere from both the above ratios and gas-to-particle conversion of nonmethane hydrocarbons to organic particulate carbon.

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Tire tread rubber in airborne particles near the road were analyzed rapidly by use of pyrolysis gas chromato-graphy. Organic compounds in asphalt particles or vehicle exhausts could interfere with this technique. After they were rinsed away with benzene ethanol (4: 1, v/v) mixture, SBR and NR in airborne particles could be determined to 0.1 μg range. Analysis time was only 30 minutes. In Niigata, concentrations of SBR were about four or five times higher than that of NR. Size distribution curves of rubber particles showed two peaks. Concentrations of rubber particles ranged from 2.0 to 3.1 μg/m3, or from 2.3 to 3.3% in total particulate matters and they decreased in snowy days. Rubber particles from tire tread decreased rapidly depending on the dis-tance from the road.

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