Atmospheric Pollution Due to Mobile Sourcesand Effects on Human Health in JapanJun KagawaDepartment of Hygiene and Public Health, Tokyo Women's Medical College, Tokyo, Japan

Following the rapid economic growth after World War II, diseases associated with environmental pollution frequently occurred due to delayed imple-mentation of countermeasures against environmental pollution. These diseases are exemplified by Minamata disease, Itai-itai disease, chronicarsenic poisoning, and Yokkaichi asthma. After multiple episodes of these pollution-related diseases were experienced, the government and the pri-vate sector made joint efforts to reduce environmental pollution. As a result of these efforts and because of changes in the industrial structure, pollu-tion-related diseases have declined. Instead, however, air pollution from automobile exhaust and the health effects of automobile exhaust on peopleliving along roads with heavy traffic began to attract the public's attention after an increase in the use of automobiles. The epidemiological surveyscarried out by the Environmental Agency and the Tokyo Metropolitan Government also have suggested unfavorable effects of automobile-caused airpollution on people living in large cities or along major roads. To solve this problem, it seems imperative to promote the reasonable use of automo-biles and to work toward more efficient transportation of goods based on analyses of city structure, the life-styles of city dwellers, and the socioe-conomic composition of cities. In addition, the discharge of pollutants from automobiles could be controlled. - Environ Health Perspect102(Suppl 4):93-99 (1994).

Key words: atmospheric pollution, automobile exhaust, health effects

Introduction

The rapid and high economic growth afterWorld War II brought environmental destruc-tion and serious health damage because ofenvironmental pollution in several severelypolluted areas of Japan. There were many

pollution-related diseases, Itai-itai diseaserelated to cadmium pollution created by theeffluent from the Mitsui Mining andSmelting Company (1,2), Minamata diseasecaused by the ingestion of fish and shellfishcontaminated with mercury compounds dis-charged from the Minamata Factory of theNew Japan Chisso Fertilizer Company(1,3), Yokkaichi asthma related to the sul-fur oxides (SOX) discharged by the petrole-um industry (1,4), and chronic arsenic poi-soning resulting from environmental pollu-tion in the areas around the Toroku andSasagadani mines (1). To provide promptand fair protection and relief to the sufferersof this pollution-related health damage, thePollution-Related Health DamageCompensation Law, which charges the pol-luters with the necessary expenses, has beenin force since 1974. However, the onset ofpollution-related health damage was pre-

This paper was presented at the Symposium on RiskAssessment of Urban Air: Emissions, Exposure, RiskIdentification and Risk Quantitation held 31 May-3June 1992 in Stockholm, Sweden.

Address correspondence to Jun Kagawa,Department of Hygiene and Public Health, TokyoWomen's Medical College, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162, Japan. Telephone 81 03 3553 8111.Fax 81 033551 3107.

vented later by countermeasures againstenvironmental pollution as a result of jointefforts by government and industry andchanges in industrial structure.

Air pollution because of automobile ex-haust and especially the health effects of autoexhaust on people living along roads withheavy traffic have become big environmentalhealth issues in Japan. Due to the excessiveconcentration of population and industryaccompanying high economic growth, therehas been an increase in traffic volume.

Environmental PollutionProblems and Preventionin JapanIn accordance with the Basic Law forEnvironmental Pollution Control, environ-mental quality standards (EQS) were set upfor sulfur dioxide (SO2) in 1969 (revised in1973), carbon monoxide (CO) in 1970, sus-pended particulate matter (SPM) in 1972,and nitrogen dioxide (NO2) (revised in1978) and photochemical oxidants (Ox) in1973 (5) (Table 1). To ensure compliancewith these standards, emission and effluentregulations came into force (Figure 1).

Health Effects fromMajor PollutantsTokyo is the capital of Japan, the mostdensely populated area of Japan, and thearea with the most automobile exhaust pol-lution. Table 2 shows the maximum 1-hrand 24-hr values of major pollutants andthe maximum number of hours or daysthat the 1-hr and 24-hr values were above a

Table 1. Environmental quality standards in Japan (5).Substance Standard values

Sulfur dioxide 1-hr 0.1 ppm24-hr 0.04 ppm

Carbon monoxide

Suspended particulatematter

Nitrogen dioxidePhotochemical oxidants

8-hr 20 ppm24-hr 10 ppm1-hr 0.20 mg/im3

24-hr 0.10 mg/im324-hr 0.04-0.06 ppm

1 -hr 0.06 ppm

certain level among 22 general air pollutionmonitoring stations and 30 automobilemonitoring stations along Tokyo roadsidesin 1990 (6,7).SO2 levels have been improved remark-

ably, compared with the peak value of0.059 ppm in 1967, because countermea-sures against SO, including the importa-tion of low-sulfur content fuel, the desulfu-rization of heavy oil, and flue-gas desulfur-ization (Figure 1). In spite of several kindsof countermeasures such as emission con-trols on stationary sources and automobileexhaust (Figure 1), NO2 levels have notimproved. Problems involved in control-ling SPM because of their origin from mul-tiple sources have caused SPM levels toremain unimproved.

Automobiles are the main source of COair pollution. As a result of gradually inten-sified restriction of CO emitted from auto-mobiles since 1966, the annual average con-centrations of CO have dropped rapidly, asshown in Figure 1. In the case of photo-

Environmental Health Perspectives 93

1950 1960 1970 1980 1990

*Itai-itai Disease *Chronic Arsenic Poisoning0 Minamata Disease (Toroku & Sasagadani Mines)

*Donora Episode *Photochemical Smog Episode* London Episode

* Yokkaichi Asthma

* Environmental Pollution Division in MHW aBasic Law for

bRegulation forAEE* Environmental Pollution ControlRegulation for AEE * * Air Pollution Control Law

* EQS for S02 (Revised, 1973)Countermeasures for SOx * 0 EQS for CO

* EQS for SPMCountermeasures for Soot and Dust M * EQS for N02 (Revised,1973)

EQS for OxEnvironmental Agency A * Pollution-related Health

Damage Compensation LawCountermeasures for NOx * (Revs sed,1988)

. S02 Chemical SubstancesControl Law

2 CO °O°xppm 12 days

5 ppm 10

4 8

3 6

2 4

1 2

19 I1 0 0 -0

Figure 1. Historical aspects of environmental pollution problems and pollution prevention in Japan (6,7).a Ministry of Health and Welfare. b Automobile exhaust emissions.

chemical oxidants, the number of days ofissuing an oxidant warning when the hourlyoxidant concentration level exceeds 0.12ppm is strongly influenced by meteorologicconditions and fluctuates considerably fromyear to year (Figure 1). Measures to controlhydrocarbon emission from stationarysources and automobiles have been promot-ed to prevent photochemical air pollution.

In 1968, the health problems related to

lead pollution from motor vehicles inUshigome Yanagi-cho, Tokyo, drew publicattention. However, it was found later thatthe analysis of lead in blood was not correct,and there were actually no cases of lead poi-soning among the inhabitants of that area.

Although the expert committee on EQS forlead conduded in 1976 that it was unneces-

Table 3. World Health Organization guidelines forprotection of the general population (8).

Averagingtime, ppm NO2 SO2 CO 03

1 -hr 0.21 0.12 25 0.076-0.18-hr 1024-hr 0.08

CO-Hb2.5-3.0%

Abbreviations: NO2, nitrogen dioxide; SO2, sulfurdioxide; CO, carbon monoxide; 03, ozone.

sary to establish an EQS for lead if the pre-sent pollution level continued, the Councilfor Industrial Structure decided to supplylead-free gasoline in 1974 and not to add leadto regular gasoline beginning in 1975 becauselead damages the catalyst installed in automo-bile engines to decrease the emission ofNON.When we evaluate health effects by com-

paring the observed concentration of majorpollutants shown in Table 2 with WorldHealth Organization guidelines (8) for healthprotection shown in Table 3, significant andclear health effects may not be expected,except in the case ofphotochemical oxidants.

Evaluation of Health EffectsDue to Exposure to CombinedAir PollutionContribution ofNitrogen Oxidesfirom Automobile Exhaust toGeneral Air PollutionAutomobile exhaust accounted for 67% ofthe total NO, emissions in Tokyo, 32% inYokohama and, 47% in Osaka in 1985(9). This suggests that automobile exhaust

Table 2. Concentrations of major air pollutants in the Tokyo metropolitan area in 1990 (6,7).(A) At general air pollution monitoring stations

SO2, ppm NO2, ppm SPM, mg/mi3 CO, ppm ox ppm

Maximum 1-hr value 0.112 0.190 0.888 16.6 0.200Maximum 24-hr value 0.040 0.116 0.196 6.3Number of hr (days) that

the 1-hr value is over 0.1 ppm: 1-hr/year overO.20 mg/m3:136-hr/month over30 ppm: none over0.12 ppm: 33 days/yearNumber of days that

the 24-hr value is over 0.06 ppm: 60 days/year(B) At automobile exhaust emissions stations

S02,ppm NO2,ppm SPM,mg/m3 CO,ppm Ox,ppmMaximum 1-hr value 0.097 0.208 0.868 23.9 0.132Maximum 24-hr value 0.045 0.094 0.307 6.6Number of hr (days) that

the 1-hr value is over 0.1 ppm: none over 0.2 ppm: 1-hr/year over 0.20 mg/m3: 151-hr/month over 30 ppm: none over 0.12 ppm: 1 day/yearNumber of days that

the 24-hr value is over 0.06 ppm: 140 days/year

Abbreviations: S02, sulfur dioxide; NO2, nitrogen dioxide; SPM, suspended particulate matter; CO, carbon monoxide; Ox, photochemical oxidants.

Environmental Health Perspectives

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1930 1940I IM4euse Valley Episode

Yokohama Asthma a

X N02* Average of 15 0.06X monitoring stations

which are in 0.05continuous operation

* National Tokyo 0.04monitoring station

U Average days per year 0.03when the hourly oxidantaverage exceeded 0.12 0.02ppm in Tokyo bay area

0.01

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Table 4. Relationship between prevalence of respiratory symptoms and air pollutants (10). a

Survey A

Male Female

N02 S02 SPM N02 S02 SPM

Adult bPersistent cough and phlegm * ** ** *Persistent phlegm ** ** ** * ** **Asthmatic symptoms

ChildrenAsthmatic symptoms ** ** * *Congestion in chest and phlegm ** * ** *

Survey B

Male Female

N02 S02 SPM N02 S02 SPM

Adult bPersistent cough and phlegm * **Persistent phlegm ** ** * ** ** *Asthmatic symptoms * **

ChildrenAsthmatic symptoms ** * **Congestion in chest and phlegm ** * * *

No mark, indicates not significant. Abbreviations: NO2, nitrogen dioxide; SO sulfur dioxide; SPM, suspendedparticulate matter. a See text about the difference between Surveys A and B. Adjusted prevalence for age andsmoking. * Level of significance is p<0.05. ** Level of significance is p<0.01.

contributes more than 50% to general airpollution in large cities in Japan.

Recent Epidemiological Surves ofHealth Effects Caused by Air PollutionSurveys by the Environment Agency. Thefollowing two surveys (10) conducted bythe Environmental Agency (EA) served asimportant sources of data used by theexpert committee (10) to assess the healtheffects of current air pollution, as discussedlater.

Survey A with Adults. From 1982 to1983, the EA surveyed 33,090 parents andgrandparents of children attending elemen-tary schools in 28 districts of nine prefec-tures who had been living for more than 3years in districts where the annual averagelevels of NO2, SO2, and SPM were 3.0 to38.0 ppb, 4.0 to 13.5 ppb, and 20.0 to63.0 pg/m3, respectively. (Data for theyears concerned were measured at the regu-lar ambient air monitoring locations.) Thissurvey revealed significant correlationsbetween the prevalence of persistent coughand phlegm in males or females and theannual average S02 and SPM levels (Table4). The prevalence of persistent phlegmwas significantly correlated with the levelsofNO2, SO2, and SPM (10).When the examined schools were divided

into three groups, group U (schools located indistricts with a population density over5000 persons/kmi2), group S (density of

1000-5000 persons/km2) and group R(density below 1000 persons/km ), theprevalence of persistent cough and phlegmproved highest in group U and lowest ingroup R (10). When the prevalence of per-sistent cough and phlegm for each year andeach sex was compared among the threegroups, hardly any significant intergroupdifferences were found. The prevalence ofpersistent cough and phlegm was analyzedin relation to the number of family mem-bers, house size, indoor air pollution level,anamnesis, occupation, and smoking. Thisanalysis revealed a significant correlationbetween anamnesis and the prevalence ofpersistent cough and phlegm, a slightly sig-nificant correlation with smoking, andhardly any significant correlation withindoor air pollution (10).When the crude prevalence of persistent

cough and phlegm was analyzed in relationto NO2 levels over 10 ppb intervals, theprevalence in both males and femalesincreased as the NO2 level rose (Table 5).The current prevalence of asthmatic symp-toms in males and females was not signifi-cantly correlated with any air pollutant(Table 4).

Survey A with Children. From 1981 to1983, a survey was made of 43,682 elemen-tary schoolchildren who lived in districtswhere the annual average levels of NO2,SO2, and SPM were 3.5 to 34.0 ppb, 4.0 to

Table 5. Comparison of crude prevalence of persistentcough and phlegm according to nitrogen dioxide (NO2)concentration (annual average) (10).a

Survey A Survey B

Males, Females, Males, Females,N02, ppb % % % %

-10 1.0 0.3 2.6 0.711-20 1.7 0.4 2.4 0.821-30 2.0 0.7 2.6 1.131- 2.3 0.8 2.0 1.1a See text about the difference between surveys A and B.

316.0 ppb, and 13.0 to 69.0 pg/m , respec-tively. This analysis revealed significantcorrelations between the prevalence of asth-matic symptoms in both sexes and the levelof NO2, between their prevalence infemales and the level of SO2, and betweentheir prevalence in males and the level ofSPM. The prevalence of chest congestionand phlegm was correlated significantlywith levels of N02' SO2, and SPM inmales and with the level of NO2 in females(Table 4). When the prevalence of asth-matic symptoms was analyzed in relation tolevels of NO2 examined over 10 ppb inter-vals, the prevalence of symptoms in bothmales and females increased significantly asthe level rose, although the prevalence ofsymptoms for a given NO2 level variedgreatly among the different districts (Table6) (10).When children were divided into three

groups (U, S, and R) in the same way asabove, the prevalence of asthmatic symp-toms and the prevalence of chest conges-tion and phlegm were highest in group Uand lowest in group R. This intergroupdifference was statistically significant.When the prevalence of these symptomswas paired with physical constitution, pastmedical history, current illness, past nutri-

Table 6. Comparison of the prevalence of asthmaticsymptoms in schoolchildren according to nitrogen diox-ide (NO2) concentration (10). a

Survey A

N02, ppb Boys, % Girls, %

-10 1.9(1.0-2.9) 1.7(0.5-4.9)11-20 4.1(2.2-6.2) 2.3(0.3-3.9)21-30 4.0)2.2-6.0) 2.8(1.2-4.5)31- 5.5)2.9-7.1) 3.1(2.5-4.1)

Survey B

N02, ppb Boys, % Girls, %-10 4.2(2.9-6.2) 2.6(0.9-3.5)

11-20 4.4(3.0-5.8) 2.8(1.2-5.5)21-30 4.5(3.2-6.0) 2.7(1.8-3.8)31- 6.1(4.2-8.7) 4.0(3.3-4.7)8 See the text about the difference between Surveys Aand B.

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tion, family composition, house size,indoor air pollution, genetic predisposi-tion, and living environment, significantcorrelations were detected for physical con-stitution, past medical history and currentillness. Following this discovery, an assess-ment was made as to whether the differ-ences in the prevalence of symptomsamong the three above-mentioned regionalgroups could be explained by these threefactors. In the case of all three factors, theorder of the prevalence of symptoms fromhighest to lowest was U>S>R, in childrenfor whom the factor was positive and inchildren for whom the factor was negative.This suggests that other factors are respon-sible for the regional differences in theprevalence of symptoms. However, whenanalyzed for each year and each sex, region-al differences were not always significant.Factors related to indoor pollution had vir-tually no significant correlation with theprevalence of symptoms (10).

Survey B with Adults. From 1980 to1984, a survey was conducted involving167,165 parents and grandparents of chil-dren attending elementary schools in 51districts of 28 prefectures who had lived inthe districts for more than 3 years. In dis-tricts where the annual average levels ofNO2, SO2, and SPM in the years con-cerned were 5 to 43 ppb, 5 to 24 ppb and20 to 90 pg/m3, respectively. Significantcorrelations were found between the age-adjusted prevalence of persistent cough andphlegm in females and the levels of NO2and SO2, although no significant correla-tions were detected in males (Table 4) (10).When the age-adjusted prevalence of

persistent cough and phlegm was analyzedin relation to the level ofNO 2 over 10 ppbintervals, the prevalence of symptoms infemales increased as the level of NO2 rose,although no such correlation was observedin males (Table 5). The prevalence of per-sistent phlegm was significantly correlatedwith levels of N02, SO2, and SPM.When the prevalence of asthmatic symp-toms was analyzed in relation to air pollu-tants, a significant correlation was observedbetween their prevalence in females and thelevel of SO2 and between their prevalencein males and the level ofSPM (10).

Survey B with Children. In the samedistricts mentioned above, a survey wascarried out from 1980 to 1984 involving98,695 elementary schoolchildren wholived in those districts for more than 3years. When the prevalence of asthmaticsymptoms was analyzed in relation to thelevels of air pollutants, significant correla-tions were found between the level ofNO2

and prevalence in males and females andbetween the level of SO 2 and prevalence infemales (Table 4). When the prevalence ofchest congestion and phlegm was analyzedin relation to the levels of air pollutants, asignificant correlation was found betweentheir prevalence in males and females andthe levels ofNO2 and SO2 (Table 4) (10).When the prevalence of asthmatic symp-

toms was analyzed in relation to the level ofNO2 over 10 ppb intervals, the prevalencein males and females was significantly high-er at NO2 levels over 31 ppb than at NO2levels below 30 ppb, although the preva-lence for each 10 ppb interval varied great-ly among the different districts (Table 6).Part of the results of Survey B were pub-lished by Tunetoshi et al. (11).

Survey by the TokyoMetropolitan GovernmentThe Tokyo Metropolitan Government (12)conducted a survey of the health effects ofcomposite air pollution in schoolchildrenfrom 1978 to 1984. When pulmonaryfunction was measured monthly during a 2-year period in 153 third-grade children (9 to10 years old) attending an elementaryschool in Nakano Ward, the growth-relatedincrease in pulmonary function was signifi-cantly lower in these children than inschoolchildren in a clean-air district inChiba Prefecture. In Nakano Ward, Tokyo,the annual average level of SO2, SPM, andNO2 in 1983 was 0.008 ppm, 0.052mg / m 3 and 0.030 ppm, respectively.From 1987 to 1989, the Metropolitan

Government (13) repeated pulmonaryfunction measurements in a larger numberof children attending two elementaryschools in center city and one elementaryschool in a control district selected on thebasis of 10-year cumulative NOX dataobtained at regular ambient air monitoringstations. This survey disclosed a significantdifference in the prevalence of wheezingand asthmatic symptoms between centercity and the control district. The growth-related increase in pulmonary functiontended to be lower in center city than inthe control district (13).

Epidemiological Surveys ofHealthEffet ofAir Pollution around Roadswith Heavy TrafficIn the report by the expert committee(10), the necessity of considering the influ-ence of regional air pollution, whichappears to be more severe than generalambient air pollution, was pointed out.This suggestion is based on the followingsurveys in roadside districts conducted in

several areas.The EA conducted a respiratory question-

naire survey on the health effects of air pollu-tion on residents living along heavy-trafficroads (traffic volume about 150,000 auto-mobiles per day) from Osaka to Kobe in1975 in cooperation with Hyogo PrefectureEnvironmental Pollution Research Instituteand Watanabe et al. (14). The subjects ofthis survey were housewives between 30 and60 years old who lived in any of the follow-ing areas for more than 2 years: within 50 mof the edge of a national road (area A) and inmore remote areas (150 to 250 m away fromthe edge of a national road [area B]). Therewere 420 subjects in area A and 429 in areaB. The prevalence of persistent cough andacute bronchitis tended to be higher in thearea A group than in the area B group. Nosignificant difference was observed in pul-monary function. In this survey, the onemonth average levels of SO2, NO 2, CO,and lead in area A were 0.025 ppm, 0.045ppm, 2.7 ppm, and 0.31 pg/im , respectively.The levels in area B were almost half thelevels in area A.

Nagira et al. (15) investigated the preva-lence of respiratory symptoms and diseasesin 2,677 schoolchildren attending two ele-mentary schools facing a national roadlinking Osaka and Kobe. Prevalence wasanalyzed in terms of the distance betweenchildren's homes and the road (within 100m, 100 to 300 m, and over 300 m awayfrom the edge of the road). A close rela-tionship was found between the prevalenceof persistent cough or phlegm, wheezing,acute respiratory infection, recurrent respi-ratory infection, or allergic rhinitis and dis-tance from the road: the closer the chil-dren lived, the greater the prevalence rate.Matuki et al. (16) investigated the use-

fulness of the urinary hydroxyproline/crea-tinine ratio (HOP ratio) as a new biochem-ical index of the adverse health effects ofpassive smoking and air pollution. A totalof 4,964 schoolchildren 6- to 11-year oldwere studied from 1977 to 1980. The areainvestigated was a typical residential regionof Tokyo with three main roads (each witha traffic volume of 40,000 to 80,000 auto-mobiles per day). The HOP ratio was ana-lyzed in terms of the distance between thechildren's homes and the main road (with-in 50 m, 51 to 100 m, and over 101 mfrom the main road) and the number ofcigarettes smoked per day in their house-hold. The HOP ratio increased withincreasing numbers of cigarettes smoked intheir household and with shortening of thedistance between their homes and the mainroad. A significant positive correlation

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ATMOSPHERIC POLLUTIONAND HUMAN HEALTH EFFECTS IN JAPAN

Table 7. Percentage of prevalence of respiratory symptoms and past history of disease in residents living alongroadsides and in more remote areas.

Roadside Remote districts Level of significance a

Respiratory symptomsPersistent cough 7.5 5.2 0.049Persistent phlegm 12.7 10.0 0.069Persistent cough and phlegm 4.5 3.4 0.231Wheezing 2.0 1.7 0.836Asthmatic attack 7.0 6.7 0.896Dyspnea 1.8 0.8 0.075

Past history of diseasePneumonia 9.9 8.0 0.164Allergic rhinitis 14.3 15.0 0.614Chronic bronchitis 4.3 4.4 1.000Bronchial asthma 0.7 0.7 1.000

a Level of significance was tested by the chi-square test.

between the HOP ratio and these factorswas found.The Tokyo Metropolitan Government

(17) examined the effect of air pollutionon residents living along heavy-traffic corri-dors where traffic volume during daytime12-hr is about 40,000 automobiles per dayfrom 1982 to 1984. The prevalence ofsymptoms was compared in 816 house-wives living along roadsides (within 20 mof the road) and 1100 housewives living inmore remote areas (20 to 150 m away fromroads). As shown in Table 7, the preva-lence of respiratory symptoms tended to behigher in the roadside group than in theremote group. A similar tendency also wasobserved when subjects were analyzed byage, duration of residence in the district,and smoking. A simultaneous environmen-tal survey revealed that levels of air pollu-tants decreased as distance from the roadincreased, suggesting the involvement ofautomobile exhaust in the high prevalenceof respiratory symptoms in the roadsidegroup. In that survey, the 7-day averagelevels in Itabashi Ward were as follows:NO, 0.071 ppm at the roadside, 0.011ppm at 20 m from the roadside, and 0.009ppm at 150 m from the roadside; NO2,0.041 ppm at the roadside, 0.021 ppm at20 m from the roadside and 0.019 ppm at150 m from the roadside; SPM, 136.6 atthe roadside, 113.4 at 20 m from the road-side, and 98.0 pg/m3 at 150 m from theroadside.

Nitta et al. (18,19) published the resultsof these studies conducted from 1982 to1984. The Mantel-Haenszel odds ratiosfor distance from the roadway, adjusted forage and smoking status, ranged from 0.80to 2.57 for chronic phlegm, chronic cough,chronic wheezing, shortness of breath andchest cold with phlegm. Both reports sug-gest that exposure to automobile exhaust is

associated with increased risk of respiratorysymptoms.Ono et al. (20,21) surveyed residential

SPM and NO2 concentrations along themajor roadways (traffic volume during thedaytime 12-hr: about 35,000 automobilesper day) in Tokyo and conducted a healthsurvey on respiratory symptoms and distancefrom roadways in 1987. Environmentalmonitoring was conducted five times, everythree or four months. Using a newly devel-oped SPM sampler and NO2 filter badge,continuous 4-day (96-hr) measurements wereconducted in 200 residential homes for 4weeks. NO2 was measured in the livingroom, kitchen, and outside each home, whileSPM was monitored only in the living room.Health information from 805 homes was col-lected using self-administered respiratoryquestionnaires. SPM and NO2 concentra-tions showed large variations. Indoor pollu-tion levels depended mostly on indoorsources such as cigarette smoking and unven-tilated space heaters, and the effect of thoseindoor sources were influenced by the build-ing structure with respect to airtightness. Anassociation between an increase in pollutantlevels and distance from roadways wasobserved. However, its effect is small com-pared to the effects of indoor sources. Theprevalence rate of respiratory symptoms washigher in children and adults in areas nearestroadways with heavy traffic. These findingssuggest the presence of a relationship betweenautomobile exhaust and health effects.To examine the health hazards of road-

side air pollution in more detail, the TokyoMetropolitan Government (22) conductedquestionnaire survey of respiratory symp-toms from 1987 to 1989. The subjects ofthis survey were women between 30 and 60years old who lived in one of the followingareas for more than 3 years: a) within 20 mof the edge of any major road in Sumida

Ward (the roadside group), b) 20 to 150 maway from the edge of major roads inSumida Ward (the remote group), and c)Higashiyamato City excluding areas within20 m of the edge ofa road (the Higashiyamatogroup). There were 489 subjects in the road-side group, 800 in the remote group, and 821in the Higashiyamato group. The prevalenceof persistent cough, persistent phlegm,wheezing, and shortness of breath from high-est to lowest was in the following order:roadside > background > Higashiyamato.When the data were corrected for age, dura-tion of residence in that location, occupation,smoking, method of indoor heating, andhouse structure, the prevalence of wheezingand shortness of breath was found to differ sig-nificantly among the different districts. Anenvironmental survey in these districts revealedthe gradients ofNO and SPM levels. Whenexposure levels were examined in about 20subjects each from the roadside group and theremote group and about 10 subjects from theHigashiyamato group, the levels of air pollu-tants during the nonheating period of theyear decreased in the following order:roadside > background > Higashiyamato.The outdoor levels of air pollutants showedno area-related gradient during the indoorheating season.

The Relationship between AirPollution and ChronicObstructive PulmonaryDiseaseThe expert committee for evaluating therelationship between air pollution and healthdamage (23) (an organization set up withinthe framework of the Central Council forEnvironmental Pollution Control) drew thefollowing conclusion about the relationshipbetween current air pollution levels and theprevalence of chronic obstructive pulmonarydisease (COPD) in Japan, based on compre-hensive assessment of the available evidencefrom animal experiments, experimentalhuman exposure studies, epidemiologicalstudies and dinical findings in 1986. a) Aswas true of air pollution in the past, present-day air pollution is mostly attributable to thecombustion of fossil-derived fuels. Therefore,it would not be a significant error if the pre-sent air pollution in Japan is dealt with interms of three major air contaminants, SO2,NO2, and SPM. Of these three, the lattertwo seem to warrant particular attention, con-sidering the current status of fuel consump-tion, countermeasures against air pollutionand changes in the source of pollutants(especially changes in the structure of trafficsystems). b) It cannot be denied that air

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J. KAGAWA

pollution as a whole has had some influenceon the natural history of COPD. From1955 to 1965, COPD in individuals livingin certain areas of Japan was chiefly attrib-utable to air pollution, on the grounds thatits prevalence was considerably higher indistricts with high air pollution levels.However, it appears to be impossible toattribute COPD to air pollution alone. c)Based on an assessment of the present levelof air pollution in Japan in relation toCOPD, we would like to call attention tothe following points: What we studied wasprimarily the effects of environmental airpollution on the population. Therefore,the effects of air pollution in particularareas, especially those with higher air pollu-tion levels than the average, must be con-sidered separately. Also, the existence of agroup of people with increased sensitivityto air pollution has been attracting atten-tion. If the number of individuals belong-ing to this group is not large enough, thisgroup may be overlooked during epidemio-logical studies on the general population.This possibility must be borne in mind.

Future TopicsThe Japanese Expert Committee (23)affirmed the possibility that air pollution inJapan is affecting the natural history ofCOPD. In its opinion, the levels of airpollution in Japan are not high enough toclearly demonstrate a cause-effect relation-ship between air pollution and COPD, butthey also are not low enough to rule out acausal relationship. The committee addedthat the influence of automobile exhauston residents living along roadsides requiresspecial consideration.During the period when coal was a

major source of energy, SOX and particu-late matter were major air pollutants.Because these pollutants affect the large air-ways that are rich in mucus-producingcells, the health effects of air pollution inthose days was represented by chronicbronchitis-like symptoms (e.g., cough andphlegm). Following the replacement ofcoal with petroleum and the increase inautomobiles, NOX and fine particulatematter (containing nitrates and sulfates)began to act as major air pollutants. In thissituation, the peripheral airways seem to bethe major site affected by air pollution.The peripheral airways are referred to as asilent zone where abnormalities are lesslikely to become apparent. For this reason,the effect of air pollution on the peripheralairways is difficult to assess.The data obtained by general ambient

air pollution surveys conducted by the

Disease

III Health

Health

Residents in City Residents in Rural Areas

Smoking

Air Pollution

Occupational Exposure

Indoor Pollution

Residents Living on Residents Living on Residents Living on Residents Living onthe Roadside the Remote District the Roadside the Remote District

Disease

III Health

Health

Auto Exhaust

Smoking

GeneralAir Pollution

OccupationalExposure

IndoorAir Pollution

Smoking

GeneralAir Pollution

OccupationalExposure

IndoorAir Pollution

Auto Exhaust

Smoking

GeneralAir Pollution

OccupationalExposure

IndoorAir Pollution

Smoking

GeneralAir Pollution

OccupationalExposure

IndoorAir Pollution

Figure 2. Evaluation of the health effects of automobile exhausts on residents living along heavy traffic roads.The scale of each item does not necessarily indicate the exact strength of the effect of each item.

Environment Agency and the TokyoMetropolitan Government do not demon-strate clearly the health effects of air pollu-tion but also do not rule out an effect as

discussed above. When roadside residentswho are thought to be exposed to high lev-els of automobile exhaust were surveyed,the prevalence of respiratory symptomstended to be higher than in more remote

inhabitants. It is an open question, howev-er, whether the residents with respiratorysymptoms were exposed to higher levels ofautomobile exhaust than symptom-freeinhabitants.To evaluate the contribution of automo-

bile exhaust to health hazards, it is necessary

to evaluate the percentage of the totalamount of air pollution to which individualsare exposed that is attributable to automobileexhaust. The effect of a given level of auto-

mobile exhaust exposure differs in individualswho are also exposed to air pollutants fromother sources and in individuals who are not

exposed to air pollutants from any othersource. When city dwellers are exposed to aircontaminated with pollutants from fixed andmobile sources to a degree close to the mini-mal exposure level presenting a health hazard,health effects appear likely to become mani-fest as they are exposed to indoor air pollu-tants or to automobile exhaust by living alongroads with heavy traffic (Figure 2).More research, including assessment of

individual exposure to auto exhaust andassessment of health effects among roadsideresidents more highly exposed to auto

exhaust, is necessary before any definitiveconclusion concerning a causal associationbetween exposure to auto exhaust andincreased risk of respiratory symptoms and

Environmental Health Perspectives

Smoking

Air Pollution

Occupational Exposure

Indoor Pollution

98

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ATMOSPHERIC POLLUTIONAND HUMAN HEALTH EFFECTS INJAPAN

diseases can be drawn. The process of healthrisk assessment (RA) on the health effects ofenvironmental pollution due to auto exhaustmay demand scientific research involvingperformance of RA, without regard to riskmanagement (RM). However, environmen-

tal pollution must not be allowed to increasewhile we attempt to perform scientific RAinstead of RM. RM should satisfy publicrequirements for foreknowledge and preven-tion of risk evaluated by incomplete RA.Furthermore, it is necessary to construct a

comprehensive and prescient environmentalpolicy, not only to prevent local pollutionand preserve the natural environment, butalso to promote human health and to createa comfortable urban environment.

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