ooilurion. 

ay 

ãån.rãipòitiqi¡.may 

ôrrildren, for example, t"uïüJ'à'i í"ú;iì;iiv increasáO-iist< fromãir poltution bv virtue of

their tifestyle patterns, *hi.;""?i.Ëi;;;1";';;;;;f houis of outdoor èxercise' regardless or

air quality, during daylight hours.

Several studies have addressed possible effects of multi-hour oxidant e*posu'e2'5' but

,,,.*pi, io'irrilö;J1.il;i"iuig'"ó"ìtv have been stymied by concurrent exposures to

other potlutantr, unrurrrr"áiärJ';;;ìt;î protäcols, or alack of detailed air monitorins at test

sites.

\ileinvestigatedmulti.houro,effectsinafieldsettinginvolvingactualambient.

exposures, while employinË'lüìriu."Jrã;"-:,;å;t r.árlr...nt tãchniques. over a six'weck

oeriod. we studied a totat ;f ï93 healthy volunteè-rs, aged 8-17 years' who,atten-dcd a summer

õamp in a mountain ro"rtion-íõo'[rn-sãutteast of Loi¡,nãetes. Some volunteers came from

extremely o.-polluted ,.giänr'ái ;i,; $;;il õó;rì (ros Ànãeres) Aif Basin; otlers came from

much cleanei areas. At the camp, ambient orconcentrationi typically a-pp-roached the primary

National Ambient ei, qualìiîttanãài¿ tÑnnqs) cðnlinttái¡on oi o'iz ppm (t20 ppb) for

several hours during the;ii;""-;;;;d òãtrv eìeîing, rhen decreased to low.but non-zero

levels overnight; particutaie'iË;;iË';;;;".siúible. Tñê investisation's main purpose was to

address the question: ¡" vã,iiäîápì!üi'üËïtt acute ct'angei in lung function related to

low-level multi'hour oxidant air pollution exposureT

*tt"?oÈ.ro 

site was located at pine Springs Ranch, a christian gamp. operatcd by the

Sourheasrern California c;i;;.;;; ïl-tt'ã 3üinttt-oai Aduentist Church' rhis 316-acre

facility is located n.., r¿íirîñàì'õÃ,-isõ-Ën., *utheaitãf ios Angelcs at an altitude of 1570

m. The camp rests in 

" 

tt,irli"Ë'üä;;;í;"1;;;Ñnà"¿ on two sidés bv mountain pcaks some

T00mhigherinelevation. Vegetationinthegeneralaiãaisdese,tsctu6brushwithoccasional

stands of pine trees. rr,e..*Ëli" óiaisic teãeptot site; no important air pollution sources are

nearby.

The movable biosurveillance facilityó was placed in a central cam-Þ, location and

continuous air quality r";i;;i;;;ì; ;ðáìil;" to lulã-funõtion testins' was performed at this

central site f rom late J"".';i;'"';fi..;ly Ai;ilt l98ti. Campers arrivéd on Sundav af ternoon

and stayed rhrough the f;ìl;;;;; Éìrïá"v ñotn^ing.' sìu¿i., were performed from Sundav

through Friday afternoo"t"åtifv,ïå"îîãi tä int.tf.t-e *ittt itiigiout oüseruance of thc sabbath'

Generalcampactivitieswerehighlystructufed.Campersandcounselorswereassigncd

to a specific cabin, and .li'iå,ip ãiiliiiË;;-ü;i;i*ã ás a cabin group' Acceptance into

the study was based upon.îiïfinJn.ti'iã-paiticip.te,.igneà informed-consent' and no health

contfaindioations (e.g., .riftäãi,-îütliþãnts tecelueãä tee'st¡irt upon acceptancc into thc

studv and an inexpensive';i[ií;r;.h ;;;ï;;;i;ii";. n tot"t or 29 j subjects - 154 bovs and

Ì'3ï¿r;il:-ïccllîrïiii ð"äïiiirã-iü.ï-e'.. ïr"" it.iJã i n ca mp morè tha n one week, f or

a total of 305 person-weelkiäîrîi,iiñãilãi)lìitàit tñtiãót.ristics aie summarized in Table I'

ThelarSestcontingentofsubjects(51%)residedinurbanareasofRiversidcandSan

Bernardino counties, which are among the most-or-nãiluted areas in.the unitcd Statcs. ozone

levets in thcse areas cxceed rhc NAAQS for ¡00 ñoiliiitl; ."t; in a tvpical vearl' These

subjects werc considered- t" ï;";;ìtùì; riJt-ór pa.st áÀúient o. exposure. At their homes'

daily peak O, concentratioîsift."li'fti".'Uããnloisiôei.Lf V highdr thän at camp' and seasonal

averase concentrarrons r";ü;'üî;ú;;".ir"äi ói rtlJrtói'-Ãnòtitt large contingent of subjects

ì!ii

;';íã

öiå

betw

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abo

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and/or between AM and PM testing, without regard to air quality. Then, repeated-measu¡ès

analyses of covariance were performed, to test \4,hether function tended to decline on days

with higher O. concentrations, averaged over a I h or 8h period before the f unction test. Next,

regression coelficients were calculated to relate each individual subject's PM FEVr (expressed

as change from AM FEV.) with O, concentration during the preceding lh or'8h period.

Finally, the possibility of c'umulativdexposure effects was explored through linear regression

analyses which related individual FEY, changes between Monday AM tests and subsequent PM

tests, with âverage O, concentrationi over the intervening periods. For computational

simplicity, the latter wire estimated by a weighted sum of 8h averages on Mondays, and 24h

averages on subsequent days, preceding PM testing. (Fridays \À,ere not included because their

non-standard activity/testing schedules would have made these estimates inaccurate).

RESULTS

Air Monitoring

Ozone levels rose gradually throughout each day, displaying a "broad peak" between

1000 and 2000 h each day (see Figure l). Daily maxima typically occurred in late afternoon

(1500-1700 h); subsequently, concentrations gradually declined to non-zero overnight ozone

levels of 25-50 ppb, Other gaseous criteria pollutants (SOz, CO, THC, NOx) were typically at

undetectable or trivial levels.

Meteorological patterns were quite stable for extended periods during the six weeks of

field operations. Each day, with sunrise, ambient temperatures quickly rose from overnight

lows of l0-15' C to daytime values of 25-35' C. Relative humidity ranged from 30-45 percent

overnight to typical daytime values in the 5-20 percent range. (The sixth and fìnal week of

field sampling did show some variation from this summer-long pattern, as thunderclouds

passed through the area, bringing a brief period of intermittent rain.) Nighttime winds varied

from 2-5 km/h. Wind speed typically inc¡eased to 8-12 km/h by 1200 h, then fell to overnight

levels by mid afternoon.

Particulate loadings were very low, ranging from I I to 54 ¡¿glm3 TSP collcctcd over 24h

sampling; particulate nitrate and sulfate usually accounted for lcss than twenty percent of this

material. Pollen and spores sampling occasionally identified a small amount of potentially :!

allergenic material, but counts did not appear to correlate in any systematic way with subjects'

test performance or reporting of symptoms.

Lung Function

Table II summarizes statistical results from the four key lung function tests for all 305

subject-weeks of data, and Figures I and 2 relate mean FEV, and PFR to O1, by camper week.

For FVC, FEV., and MMFR, the best overall performance'was observed ãt the Sunday PM

screening, despíte the fact that subjects were unfamiliar with the procedures. Mean FVC and

FEVn showed highly significant downtrends from Mondays through Wednesdays, with partial

reveisal on Thursdays and Fridays. Changes from AMto PMalso varied consistcntly bctwecn

days; changes were negative early in the week, and positive later. MMFR did not vary

significantly over time, Mean PFR increased significantly from one day to the next, and was

significantly higher in afternoons than in mornings. Regression analyses of individual data

showed that increases in PFR were associated with decreases in time to PFR. Individualized

regression analyses also showcd an association between increased time to PFR and increased

FEV.. However, its magnitude was too small to cxplain much of the time-variability of FEV,t.

Wheri the FEY, analyses were repeated after excluding subjects \rrith suboptimal performancè

a

a

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e

l

V

c

g

o

p

s

f

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a

a 

m

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b

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a

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o

d

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e

p

f

m

s

s

r

w

f
most of them came from relìgious, highly health-conscious families, but that factor would

nàïi¡ietV influence their sensítivity to-Or. Other consistcnt differences between our subjects

and eastern campers are not obvious at present'

Eastern camp studies differed appreciably from ours in environmental factors other

than air quality, inèluding lower attitudè (¡equiiing less ventilation for a given work rate),

higher reiative-úumidity (increasing heat stress_at aypical daytime.temperatures), and more

iiãquenrtàin (giving riõeìo more dènse vegetation, ànd thus to a different, perhaps heavier,

buiàen of aeròãttergins). That these factõrs influenced response to O, seems unlikely, but

ðannot Ue ruled out] Oí more concern is the possibility that other pollütants exacerbate the

response to Ot.

Acid aerosol coexisting with O, has been suggested as a cp¡tributor to respiratory

dysfuncLion, on the basis of su-mmer resþiratory morbidity statisticsrras we,ll as summer camp

fínãincs3. Some animal studies also indicate ihat acids enhance the respiratory toxicity of

O.12. -But c6ntr9lled human exposure studies, using much the Same response measures as

r-u'¡¡¡¡¡.r camp studies, tend to iefute the hypothesis that acid contributes to respiratory

áVitunòtion.'Several investigators have found iittle effect of exposure to sulfuric acid alone,

ai¿ flit-fe added effect of expiosure to Or plus sulf uric acid as compared to Or alone, in healthy

ádult volunteersl3. In younger asthniatics, only sligh.t, lung function clianges have been

iJpoite¿ in exposures to sulfu¡ic acid aeiosol- alonera. On the other hand, contròlled

eibirimental eiposutes might have underestimated the possibility o-f. Otlacid interactions,

because they \r'ere of shorter duration than typical summer-camp amb¡ent exposures.

Specific on-site monitoring of acid aerosols u,as not available here nor in some of the

eastern itudies. However, elevãted acid concentrations often accompany.elevated 03

concentrations at eastern camp sites. In our study, acid concentrations should have been

consistently near zero, since párticulate, NO", and SO, levels were consistently low.

We therefore conclude that time-dependent effects unrelated to air quality may

confound the interpretation of air pollutioñ effects as studied in summer camps or other

arbient-e*po.ure séttings involving iepeated lung function measurements. Past findings need ..

to be ¡eexamined in thñ light, and fúture studiès need to be designed so that time'related

effects and exposure-related effects can be distinguished in subsequent analyses.

ACKNOWLEDGMENTS

Thc authors thank Elder Stephen Blue of the Southeastern California Conference of

Seventh-Dat Adventists, Camp Ranger Rishard Gore, and the cntjre staff_of Pine Springs

Ranch for their cooperaiion and assistance with this project. We thank L'H. Wightman' J-E.

Hãm¿t, J,C. Solomori, and the entire staff of the Ranðho-Los Amigos Env-ironmental Health

Seivicé for technicaliupport. We thank Dr. M.P. Jones of the University of Iowa and Dr. D.\Y'

Dockery of Harvard Uiiversity for statistical advice relevant to this project'
14.3 r 1.3 11.5 r 1.9

1ó5r6 150r12

57 r 13 42 r'13

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age, ylr 9.1 r 0.7 11'4 r 1.'l

holght, cmr 138 t I 149 t 9

uelght. kg 32 t 6 42 t 13

rBoys and girLs cqÍbined.

11.0 r O.E 11.0 t 1.4 11'ó r 1.4

14ór6 149r11 152r10

37rg 41t12 41r11

2559 t744 2230 t 662 4374 t t690 2732 x t003

25t3t747 2t92t666 4402tt687 27ll t 1007

24gg t745 2185 t677 4377 t t757 2722 t 1058

2488 r ?38 2l1l t 67l 4471 t 1695 2736 t t059

2473 il752 2162 t 6'16 4397 t 1808 2732 * t056

247t i¡753 2t53 t 674 4483 t 1744 2706 t 1057

2469 t756 2l4l t672 4422 r. l8t0 2643 ! t053

248r ir76l 2158 t672 455E * l78l 2704 t 1081

2476 t774 2154 *.687 4489 * l80E 2687 f 1068

2495 t77l ?l75 r.684 4588 t t630 272t t t078

Perc

Perc

O, p

Age

Heig

TABLE II LUNG f unction results (mean I s'd') for 305 subjects;

results of analyses of variance comparing across days and times'

Dav Time FVC (mL) FEVl(d) PFR (mlls) MMFR lmlls)

Sun.+ p.m, 2596 t763 2272 t649 4450 t 1589 2853 r 967

Mon. a.m.

p.m.

Tue. a.m.

p.m,

Wed. a.m.

p.m,

Thu. a.m.

p.m.

Fri, a,m.

p,m.

P (day)*

P (time)

P (interaction)

0.0003 0.170

0.0000 0.331

0.295 0.077

+Slo

for 

chan

mos

*Pro

0.01

0.0000

0.32t

0,0056

0.0000

0.391

0.0026

rsunday p.m, (screening) data not included in analyses of variance'

+Huynh.Feldt adjustments were applied in calculating P values, when data distributions did

not iit assumptions underlying conventional analysis of variânce' P values < 0'00005 tabulated

as 0.0000.
Tuesday p.m. -56 66

Wednesday p.m. -78 64

Thursday p.m. -75 63

+7

+28

+16

-0.97

- 1.68

-1.46

-.067 .24t

-.1 l I .039

-.093 . 104

l0
T

1I V]L

I ti..

' ll

WEEK J: 4E SUBJECTS ÀGE 10-12, SÍART 7-10-66

oJ (-)

wEÊK 4: 47 SUBJECTS AGE 10- I 2, START 7- I 7-8E

21 00

2000

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2000

1900

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WEEK 5: 61 SUBJECTS aGE 10- I 2, START 7-24-88 IVEEK 6: 51 SUEJECTS AGE 1J+, START 7_J1_6E

PP8

160

120

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40

0

iiijiji 'lir

FIGURE 1

2200

21 00

2000

PPB

r60

120

EO

4Ô

3200

3100

:i

ì

i

ì

I

ä

1900 0

fu Fr Su Mo lu

DAY (ANII HOUR) 0F l^IEEK

FEV,, and hour'ly ozone as functjons of time, mean:i one standard error;

opeft synbols indìcate Sunday screening data,

I2

FIGU

rh

T

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l'.l tl T

ï

Ì.. IT