Environmental Health Perspectives

Vol. 79, pp. 1 79-185, 1989

Acute Lung Function Responses to

Ambient Acid Aerosol Exposures in

Children

by Mark E. Raizenne,* Richard T. Burnett,* Bonnie Stern,*

Claire A. Franklin,* and John D. Spenglert

We examined the relationship between lung function changes and ambient acid aerosol episodes in

children attending a residential summer camp. Young females (112) performed daily spirometry, and

96 were assessed on one occasion for airway hyperresponsiveness using a methacholine bronchoprovocation test. Air quality measurements were performed on site and four distinct acid aerosol

episodes were observed during the 41-day study. The maximum values observed during the 41-day

study were: 03 at 143 ppb; H2SO4 at 47.7 ,ug/m3; and [H+i at 550 nmole/m3. Maximum decrements

of 3.5 and 7% for FEV1 and PEF, respectively, were observed to be associated with the air pollution

episodes. There was some evidence of a differential lung function response to the episodes where

children with a positive response to a methacholine challenge had larger decrements compared to

their nonresponsive counterparts.

Introduction

Ambient acid aerosols resulting from atmospheric

transformations of primary pollutants may represent

a significant health hazard (1). Acid aerosols are often

observed to be associated with other air pollutants including ozone (03), nitrogen oxides (NOx), and sulfur

dioxide (SO2) (2). There have been few epidemiological

studies that have specifically addressed the acidic

aerosol-health effect hypothesis. Although no one

study has clearly associated acid aerosols with observed

adverse health responses, there is mounting evidence

from both toxicological and clinical studies that suggest that moderate exposures to air pollution mixtures

can influence respiratory health and function (2).

Air pollution episodes have been observed to be associated with acute mortality and acute and chronic

respiratory morbidity (3). Evidence that acute respiratory health and function in children is affected by

ambient air pollutants at or near current air quality

standards has been reported by several investigators

(4-11). Although the biological evidence for these

associations resides principally in transient decrements of lung function, the implications of repeated

*Department of National Health and Welfare, Health Protection

Branch, Ottawa, Canada KiA 0L2.

tHarvard School of Public Health, Boston, MA 02115.

exposures and subsequent decrements on human respiratory health remain to be determined. It is not clear

at the present time whether these changes have causal

consequences in the development or promotion of lung

disease.

Summer camps have been used by several investigators to assess the influence of ambient air pollution

on respiratory health and function of children. Because children are predominantly outdoors and relatively active while at camp, they provide a unique

opportunity to assess the relationships between respiratory health and function and concurrent air pollution levels. Raizenne et al. (10) have reported shortterm decrements in the lung function of children attending a residential summer camp in a region receiving a mixture of air pollution, including acid

aerosols. Lung function decrements were associated

with 03, fine particles (PM2.5), sulfates, and temperature. These decrements were also observed to be associated with 12- and 24-hr time lags. Other investigators

(7,8,11) have also reported observing decrements in

lung function in children at camps to be related to

ambient air pollution levels. In one study (7), the decrements were most strongly associated with 03 and

were reported to persist for up to 1 week after a 4-day

pollution episode having a mixture of pollutants including acid aerosols. Other recent studies indicate

that persistent lung function decrements are observed

in children after an air pollution episode where S02
RAIZENNE ET AL.

and total suspended particulates exceeded 200 gg/m3

(12,13).

The present study was undertaken to examine the

relationship between acute exposure to ambient pollutants including 03, fine particles (PM2.5), sulfates, and

sulfuric acid (H2SO4) and respiratory function in

children.

Methodology

A residential Girl Guide camp located on the north

shore of Lake Erie, 50 km southwest of Hamilton,

Ontario, was used in this study. There were three consecutive 2-week sessions between June 29 and August 9,

1986. One hundred forty-five young girls between the

ages of 8 and 14 were contacted, and 116 agreed to

participate in the study activities. Parents were asked to

complete a self-administered questionnaire on the

child's respiratory health history, parental health, and

household characteristics.

Spirometry was performed each day in two mobile

trailers located on the camp site. Four 21E Pulmonary

Function Workstations (Gould Medical Products,

Dayton, OH) were operated by four experienced technicians. The method of testing followed the ATS (14)

and GAP (15) spirometry guidelines for testing of

children and incorporated a minim'um of five maneuvers (16). Children were tested each day between 3:00

P.M. and 5:30 P.M., in a seated position and with noseclips

in place. Children came to the test site at approximately

the same time each day (± 30 min). Spirometers were

calibrated each day before testing and whenever the

ambient temperature changed by 20C during the

testing session. Calibration was' performed by" each

technician using a 3-L syringe. All lung measurements were corrected to BTPS (body temperatur'e, pressure, saturated) values. Height and weight -were measured at each of the first four lung function tests, and

the mean of the four measurements was used to define

a unique height and weight for each child.'

Methacholine bronchial challenge (MCh) tests were

performed on the third or fourth day of each session at

the camp site. All parental questionnaires'* were

reviewed by attending physicians at the site prior to

the test. Children with a history or current symptoms,

i.e., persistent wheeze, asthma, allergy, and recent colds,

were scheduled early in the day to monitor possible

latent responses. All tests were conducted between 8:30

A.M. and 5:00 P.M. The method of Hargreave et- al. '(17)

was used for all bronchial challenges. The maximum

concentration used was 16 mg/mL and the'maximal

response for termination of the test was a 20%

decrement in FEV1. The concentrations of methacholine inducing a 20% decrement in FEV1 (PC20FEV1)

were obtained, and positive methacholine tests (MCh+)

were defined as children having a PC20FEV1 of 8

mg/mL or less. All spirometric assessments associated

with the methacholine challenge were performed on

two 8-L Collins (Braintree, MA) water-filled spirometers, calibrated each day using a 3-L syringe.

To determine atopy, skin tests were performed using

the prick method. Ten common allergens (Table 1) were

used, along with negative (diluent) and positive

(histamine, 8 mg/mL) controls. Wheal diameter was

measured by ruler and caliper and recorded to the

nearest 1 mm. A wheal diameter 2 mm or more larger

than the response to diluent was regarded as a positive

test

An air pollution monitoring station was operated

on-site in a van situated in an open area approximately 10 m from the lung testing trailers. The air

pollution trailer housed continuously recording 03,

SO2, NO2 monitors, and a thermal speciation flame

photometric unit (modified Meloy 285) (18), which

measured continuously total sulfate (CSO42-) and H2SO4

(da . 2.5 gm). Ambient air samples for the continuous

monitors were made through a Teflon and glass filter

mounted from an inlet situated on the roof of the

trailer approximately 5 m from the ground. Tenminute and hourly averages were obtained from the

continuous monitors. Two Beckman dichotomous

particle samplers located on the roof of the trailer

sampled fine (da . 2.5 gim) and coarse (2.5 < da . 10 gm)

particle mass sulfate and elements using teflon filters.

Aerosol strong acidity ([H+] nmole/m3) and particle

sulfate (SO2-) were determined from fine particle mass

collected by a Harvard impactor using Teflon filters

with ammonia denuders (19). Organic and elemental

carbon were measured with a second Harvard

impactor using prefixed quartz filters. Two 12-hr

samples per day (starting 7 A.M. and 7 P.M. EST) were

collected from each particle monitor. Meteorology parameters, temperature, dew point, and wind speed and

direction were monitored continuously with an

hourly averaging point time using a Climatronics

modular WM-111 system. Table 2 summarizes the

aerometric measurements and the exposure metric

definitions. The percent data capture during the 41-

-day period equaled or exceeded 95% for all parameters.

The influence of air pollution episodes on the lung

function of children was examined by determining

the difference in lung function for each child between

days of high and low pollution. Four distinct

intervals of elevated air pollution and the corresponding control days are identified in Table 3. Control days

were defined as days with 03 max < 80 ppb; SO2- < 15

Table 1. Skin prick test: Allergens.

Alternaria tenuis

Aspergillus f'umigatus

Cat hair/epithelium

Dog hair/dander mix

Dust mite (Dermatophagoides farinae)

Grass pollen

Hormodendrum cladosporiodes

Horse hair/dander

Ragweed pollen

Tree pollen

180
ACUTE LUNG FUNCTION RESPONSES TO ACID AEROSOL EXPOSURE

Table 2. Pollutant exposure metrics.

Pollutant, units Method

03, ppb Chemilumninescence

1 hr maximum is maximum hourly

value for 12-hr period, 7 A.M.-7 P.M.

PM 2.5, Ag/m3 Dichotomous sampler

12-hr integrated sample (mass),

7 A.M.-7 P.M.

SO4, Ag/m3 Harvard impactor (with denuder inlet)

[H +], nmole/m3 12-hr integrated sample, 7 A.M.-7 P.M.

Total sulfate and aerosol strong acidity

H2SO4, Ag/m3 Modified Meloy 285 [Allen et al. (18)]

Flame photometry

Continuous (10 min/1-hr averages)

Temperature, OC Mean of hourly measurements over

12-hr period, 7 A.M.-7 P.M.

Relative humidity, % Average % relative humidity over

12-hr sampling period, 7 A.M.-7 P.M.

,ug/m3; H2SO4 < 10 gg/m3 (or [H+] < 55 nmole/m3).

Note that there were two episodes identified in session

2. The difference between the lung function response on

the episode day and the average of the responses on the

corresponding control days was determined for each

child and each of the responses separately. The

distribution of these differences across children was

examined. The mean of the differences were then tested

to differ from zero by a one-sided t-test. A similar

procedure was performed separately by methacholine

response.

Results

Subject characteristics are presented by session in

Table 4. A total of 112 children (77.2% of contacted)

participated in the study. Of those initially contacted,

20% refused to participate, one never attended, two left

camp early, and one subject withdrew from the study.

Five children were reported to have doctor-diagnosed

current asthma (from parental questionnaire), five

did not perform the methacholine and allergy test, and

six children did not perform either the methacholine

or the allergy test. Excluding the five asthmatics, a

cohort of 96 children had complete data on all health

components.

For the 107 nonasthmatic girls with daily lung

function results, a summary of the daily lung function responses is presented in Figure 1, where the

average residual value from each child's own mean

across days is displayed for each day (± 2 SE). For each

session, the mean values for FVC, FEV1, and FEF25-75

exhibit a U-shaped pattern over time in which the

average on the first day was larger than the other days.

A rapid decrease in function was observed initially,

with a subsequent more gradual recovery. This pattern

was not observed for peak expiratory flow (PEF), and

there was evidence of increasing values in the daily

means in the latter portion of the third session.

Methacholine bronchial challenge (MCh) was successfully completed by all subjects in the cohort of 96

children. Thirty-nine children (40.6%) had a positive

response (MCh+). Atopy to one or more of the 10 inhalant allergens noted was observed in 47 of 96 children, or 49% of the cohort. Twenty-one of 96 children

(21.8%) had both positive methacholine and a positive

atopy assessment.

The influence of MCh+ on lung function parameters

(FVC, FEV1, and PEF) was examined (Table 5). It was

observed that children with MCh+ tests had smaller

mean values for all three lung function parameters

after adjusting for age and height. The effect of atopy

was observed to have no significant influence on lung

function.

Air pollution during the study period displayed

day-to-day and diurnal variation. During each of the

2-week camp periods, four distinct pollution events

were observed. During these events, maximum 1-hr

03 concentrations exceeded 100 ppb; 12-hr [H+] ion

concentrations exceeded 100 nmole/m3. More than

half of the particle mass during these events were sulfates. The ambient levels of NO2 and SO2 were low, with

the maximum 12-hr concentrations of these gases

being 10 ppb, and no single hour exceeding 25 ppb.

These reflect the remoteness of the camp from local

stationary and mobile sources.

The most intense air pollution event began to develop

in the late morning of July 24, when 03 and cSO2- c4

concentrations increased sharply. After dropping

Table 3. Pollution episode and corresponding control days.

Episode Type of Pollution levelsa

Session number day Date 03 max, ppb [H +], nmole/m3 SO ,,gm

1 I Control' June 29-July 3 78 32 9

Episode July 6 128 321 49

2 II (a) Control' July 13-16 79 49 8

Episode July 18 133 100 14

2 II (b) Control' July 13-16 79 49 8

Episode July 25 143 559 83

3 III Controlb July 27-31 79 53 14

Episode August 6 108 306 54

a03 max, from highest hourly value 12-hour data set; [H ] and SO4'- from Harvard impactor data set.

bMaximum value across all control days.

181
RAIZENNE ET AL.

Table 4. Sample size and cohort characteristics by session.

Session

Characteristic I II III Mean

n = 112 53 32 27

Age, yearsa 11.6 11.5 11.7 11.6

Height, cma 151 146.2 148 149

Weight, kga 44 41 43 43

aMean values.

slightly overnight, the levels increased again on July

25, reaching a maximum between noon and 1:00 P.M.

03 concentrations were 143 ppm, particle sulfates

(CS02-) exceeded 100 gg/m3 with approximately half

(47.7 ,ug/m3) in the form of H2SO4 (Meloy 285 data).

During the most intense portion of the episode, H+ ion

concentrations averaged 550 nmole/m3.

The correlations between daytime (12-hr) pollutants

are presented in Table 6, and indicate a high degree of

correlation between PM2.5, S02- and H+; however,

0o100

0 050

FVC

(L) 0

-0-050

-0-100

0I100

0 050

0

- 0-050

- 0100

0-4

0-2

0

-0-2

-0-4

0.20

0O10

0

-0o10

-0 20

Is

T I1

Table 5. Height and age-adjusted mean pulmonary function

responses by methacholine responsiveness.

Methacholine

Function MCh- pa MCh+ Mean

FVC, L 2.66 0.029 2.54 2.62

FEVI, L 2.36 0.003 2.21 2.30

PEF, L/sec 5.61 0.001 5.18 5.43

n 57 39 96

aTwo-sided p-value for testing difference between MCh- and.MQh +.

Table 6. Pearson correlation coefficients for

daytime (12-hr) aerometric data.

Relative

SO4- [H+1 03 max Temperature humidity

PM 2.5 0.97 0.95 0.78 0.32 0.37

SO4- 0.96 0.82 0.30 0.36

[H + 1 0.80 0.37 0.29

03 max 0.48 0.52

Temperature 0.30

temperature and relative humidity were weakly

correlated with the air pollutants and each other.

Nighttime correlations were observed to be marginally

reduced compared to daytime values. Daytime values

are graphically presented in Figure 2. More details on

the monitoring data can be obtained from Spengler et

al. (20).

The influence of air pollution on lung function was

examined by comparing children's responses on the

day of a major pollution episode to the mean of the

responses on corresponding days of low air pollution,

termed control days. Table 7 gives the average change

in lung function between the episode and the control

days for children with positive and negative methacholine responses. A further response, II(c), was defined

relating to episode II(b) in Table 6 and is given by the

difference between the lung function responses taken

the morning after episode II(b) and the average of the

control days used for II(a) and 11(b). For FEV1, there

was a tendency for the lung function responses on the

day of the episodes to be less than the responses on the

corresponding control days except for the episode in the

third session, in which an increase in function was

observed. The children with positive methacholine

responsiveness were observed to have larger

decrements in function during the episodes than their

nonresponsive counterparts (Table 7). A similar

pattern was observed for PEF (67-143 mL/sec decline).

For both responses (FEV1 and PEF) the largest

decrements were observed on the morning after the

July 25 episode in session 2 where FEV1 declines of 80

mL, and PEF declines of 383 mL/sec were observed.

29 3 7

JUN JUL

II 15 19 23 27 31 4 8

AUG

DATE (1986)

Fi(;tJRE 1. Standardized lung function measurements by date. I (+)/(-),

standard errors.

Discussion

To date, most health studies have reported ambient

acid concentrations, primarily H2S04, to be in the

range of 2 to 10 ,ug/m3 using the continuous flame

FEV1.0

(L)

PEF

(Usec)

FEF25 75

(Usec)

182

I
ACUTE LUNG FUNCTION RESPONSES TO ACID AEROSOL EXPOSURE

occasion and to exceed 20 gg/m3 for H2SO4 on at least

two other occasions during the 41-day summer period.

The initial analyses of the effect of episodes on acute

pulmonary function indicate that only small changes

in pulmonary function may be observed to occur with

episodes of air pollution having high concentrations

of acid aerosols. Although the magnitude and temporal

characteristics of these changes are modest, they appear

consistent with other studies where acute and/or per-

*Before and After sistent declines in lung function are associated with

Data Missing specific air pollutants. The study also demonstrates that

frequent and prolonged episodes of relatively high

concentrations of acid aerosols do occur in the summer

period in Southwestern Ontario.

R.H. 7U - \| l

(0/0) 60

50

29 2 5 8 11 14 17 20 23 26 29 4 7

JUN JUL AUG

DATE (1986)

Fi(t;Rvi 2. Environmental factors by date.

photometric technique and/or equivalent units when

the titratable acid method is used (H+, nmole/m3). In

the present study, continuous ambient acid measurements were observed to attain 47.7 tg/m3 on one

Lung function measurements throughout the three

camp sessions were remarkably stable for all indices. In

all three sessions, the first measurement was significantly larger than the mean of the last nine tests. There

was evidence that larger, older children produced acceptable data more frequently on the first day. However,

when we examined the children with complete data on

all days, the difference on the first day remained significant. This suggests that for this study, the first

measurement may not be a reproducible value and

may not be a representative value of baseline lung

function. There is also evidence of a pattern in lung

performance, in all three sessions, where the initial

values for FVC, FEV1, and FEF25-75 are high, decrease

for a few days, and then increase and stabilize for the

rest of the session. The pattern differed for PEF, where

the measurements appeared stable in the first two

sessions but deviated in session 3, when it appeared to

progressively increase with time. The third session

data are discussed later. There appears to exist a day of

camp effect where similar trends in lung measurements by day occur across the three independent

sessions. The reason for this trending is not evident,

and the influence of this trend will be examined in

future analyses.

Table 7. Change in FEV, and PEF between episode and control days

by methacholine responsiveness.

FEVI, mL PEF, mL/sec

MCh- MCh+ MCh- MCh+

Episode (n = 57) (n = 39) (n = 57) (n = 39)

I -34 -48 -79 -67

(July 6) (0.008)a (0.041) (0.113) (0.228)

II (a) -49 -59 30 -135

(July 18) (0.022) (0.170) (NA) (0.189)

II (b) 3 -66 -57 -143

(July 25) (NA)b (0.144) (0.270) (0.218)

II (c)c 5 -80 -91 -383

(July 26) (NA) (0.142) (0.191) (0.039)

III 10 39 109 211

(Aug. 6) (NA) (NA) (NA) (NA)

aOne-sided p-value from one sample t-test to test if change is negative.

bNA, p-value not appropriate, since change is positive.

CDffference in lung function value between day after episode II(b) and

control days.

500

400

300

200

100

0

80

60 -

40 e

[H+]

(nmoles/m3)

s04g

(jAg/r3)

20

0

PM2.5

(Ag/M3)

140

120

100

80

60

40

20

0

rH V,6I I -"/",OI .

*.Il Il<

r-i I~~~~~~~~~~~~~~~j

140

120

03 100

max

(ppb) 80

60

40

78

74

Temp.

(oF)

70

66

62

183

-1 -rw/,
184 RAIZENNE ET AL.

The influence of a 4-day episode when 03 concentrations exceeded 150 ppb has been reported to have been

associated with decrements in PEF measurements and

that this decrement persisted for a period of 5 to 7 days

in children attending a summer camp (7). Persistent

decrements in various lung function indices have

also been associated with episodes of total suspended

particulates and SO2 (12,13). Although the design of

these latter studies differed markedly from those of

Lioy et al. (7) and from the current study, they all

demonstrated a persistent decrement in lung function

following an air pollution event. This type of response

may account for the low PEF values and the subsequent increase, or recovery, noted in the third session.

The PEF data for the third camp were unexpected

results. The measurements of PEF in the first few days

of session 3 may not have been representative values, as

the children came from the Hamilton area, and they

would have been exposed to the polluted air mass that

affected the region. There is evidence that this air mass

extended as far as Toronto (21), and Hamilton is situated between Toronto and the camp site. Furthermore,

Hamilton is known to have significant local sources of

air pollution (22), and the pollution profile in the

Hamilton region during the event may have been

more intense.

In this study, we observed that PEF was decreased on

the day of, and on the morning following, the session 2

episode. If we assume a similar response in children

originating from Hamilton, and assume a persistent

decline to be present when the children arrive for the

third session, then the initial PEF data for the third

session may be evidence of a persistent decrement and

subsequent recovery from the episode that occurred 5 to

7 days previous to the positive trending in the PEF

values in the last session. As shown in Figure 2, the

pollution profile indicates that 03 was near the 150 ppb

level (143 ppb) and that high aerosol acidity was also

present during the July 25 event. Although the association between decrements in PEF and 03 is significant in the Lioy et al. study, the authors note that other

pollutants, including acid aerosols, may have contributed to the persistent decline observed.

Chamber studies have provided evidence that adolescent children, particularly asthmatic children, may

be especially sensitive to levels of air pollution periodically observed in various ambient settings. Avol et al.

(4) exposed children to ambient oxidant air pollution

and reported significant decrements in lung function.

Koenig et al. (23) have reported evidence of decrements

in lung function of young asthmatics when exposed to

H2SO4 aerosols at 100 ,ug/m3. Further preliminary

evidence by the same author was presented at this

symposium, which indicate altered lung mechanics at

concentrations of H2SO4 of 68 ,ug/m3 (24).

Chamber studies have also demonstrated enhanced

pulmonary mechanical responses to SO2 and 03 when

exposures are coupled to controlled exercise regimes

(21). Utell (25) notes that exercise potentiates pulmonary responses to H2SO4 pollutants, particularly in

asthmatics. Planned activities during the camp did

not include events that required vigorous activity and

exertion. The absence of regular, vigorous activity

events may have been a significant factor mediating

the daily, and episode, lung function responses of the

children. At the peak of the July 25 episode, 12 subjects

performed pre- and postexercise spirometry (26). For

the group, postexercise FVC and FEV1 were observed to

increase on control day tests and to decrease on the

episode day. The magnitude of this difference, however, was not observed to be statistically different. The

expected direction and magnitude of changes in lung

function after an air pollution episode appear consistent with evidence of changes in lung function in

highly controlled chamber exposure studies to various

air pollutants.

Airway hyperresponsiveness is a common characteristic of asthma. However, there is evidence of nonspecific airway hyperresponsiveness being present in

nonasthmatic, asymptomatic populations (27). In

addition, recent evidence has suggested that nonspecific bronchial responsiveness may reflect a predisposition to the development of chronic obstructive lung

disease (28). We observed that 40% of our nonasthmatic children had MCh+ tests and that 33% of these

children had no histories of chronic respiratory

symptoms. We also noted that lung function changes

due to the episodes in the MCh+ group, in the first two

sessions, were consistently negative and, in general,

larger than the decrements in the MCh- group.

In Table 7, 8 of 10 lung function responses in the

MCh+ group are negative, while 5 of 10 are negative in

the MCh- group. We further note that after adjusting

for age and height, MCh+ children had lower lung

function and greater day-to-day variability (data not

given) in all lung function indices when compared to

the MCh- group. These preliminary results do not

permit definitive statements on the susceptibility of

methacholine sensitive subjects to be made; however,

there are indications in these data of differential lung

function profiles and responses to air pollutants in

children with and without airway hyperresponsiveness. Further analyses are currently directed in

examining these differences and their relationships

with air pollution.

We thank the children attending Camp Kiawa, their parents, the

Camp Kiawa staff, and the Hamilton Girl Guide Council for their cooperation throughout the study. Special acknowledgment is extended

to Drs. M. Sears and E Hargreave and their co-workers at St. Joseph

Hospital in Hamilton; the health field staff, J. Mortimer, C. Jette, T.

Vlad, S. Dent; the aerometrics field staff, U. Allen, M. Wolfson, P.

Koutrakis, T. Dhmyagn; our data analysis statistical associates, J.

Kearney and D. Haines; and to E Marier for her assistance in preparing

the manuscript.

REFERENCES

1. U.S. Congress. Acid Rain and Transported Air Pollutants;

Implications For Public Policy. Office of Technology Assessment,

OTA4204, Washington DC, June 1984.
ACUTE LUNG FUNCTION RESPONSES TO ACID AEROSOL EXPOSURE 185

2. EPA. An Acid Aerosols Issue Paper: Health Effects and Aerometrics, ECAO-R-0140, Environmental Protection Agency,

Research Triangle Park, NC, 1987.

3. NRC. Epidemiology and Air Pollution. Committee on the Epidemiology of Air Pollutants, Board on Toxicology and Environmental

Health Hazards, Commission on Life Sciences. National Academy

Press, Washington, DC, 1985.

4. Avol, E. L., Linn, W. S., Shamoo, D. A., Valencia, L. M., Anzer, U. T,

Venet, T G., and Hackney, J. D. Respiratory effects of photochemical oxidant pollution in exercising adolescents. Am. Rev.

Respir. Dis. 132: 619-622 (1985).

5. Lebowitz, M. D., Holberg, C. J., and Dodge, R. R. Respiratory

effects on populations from low-level exposures to ozone.

Presented at 1983 Annual Meeting of Air Pollution Control Assoc.,

Atlanta, GA, June 1983.

6. Linn, W. S., Avol, E. L., Shamoo, D. A., Whynot, J. D., Anderson,

K. R., and Hackney, J. D. Respiratory responses of exercising

asthmatic volunteers exposed to sulphuric acid aerosol. J. Air

Pollut. Control Assoc. 36: 1323-1328 (1986).

7. Lioy, P. J., Vollmuth, T A., and Lippmann, M. Persistence of peak

flow decrement in children following ozone exposures exceeding

the national ambient air quality standard. J. Air Pollut. Control

Assoc. 35: 1068-1071 (1985).

8. Lippmann, M., Lioy, P. J., Leikauf, G., Green, K. B., Baxter, D.,

Morandi, M., Pasternack, B. S., Fife, D., and Speizer, F E. Effects

of ozone on the pulmonary function of children. Adv. Mod.

Environ. Toxicol. 5: 423-446 (1983).

9. McDonnell, W. F, III, Chapman, R. S., Leigh, M. W., Strope, G. L.,

and Collier, A. M. Respiratory responses of vigorously exercising

children to 0.12 ppm ozone exposure. Am. Rev. Respir. Dis. 132:

875-879 (1985).

10. Raizenne, M. E., Burnett, R. T., and Spengler, J. D. Acute

respiratory health effects in asthmatic and non-asthmatic children

associated with ozone and fine particles (PM2.5). Submitted.

11. Spektor, D., Lippmann, M., Lioy, P., Thurston, G., Citak, K., James,

D., Bock, N., Speizer, F., and Hayes, C. Effects of ambient ozone on

respiratory function of active normal children. Am. Rev. Respir.

Dis. 137: 313-320 (1988).

12. Dassen, W., Brunekreef, B., Hoek, G., Hofschreuder, P., Staatsen,

B., de Groot, H., Schouten, E., and Biersteker, K. Decline in

children's pulmonary function during an air pollution episode. J.

Air Pollut. Control Assoc. 36: 1223-1227 (1986).

13. Dockery, D. W., Ware, J. H., Ferris, B. G., Jr., Speizer, F. E., and

Cook, N. R. Change in pulmonary function in children associated

with air pollution episodes. J. Air Pollut. Control Assoc. 32: 937-942

(1982).

14. ATS statement-Snowbird Workshop on Standardization of

Spirometry. Am. Rev. Respir. Dis. 119: 831-838 (1979).

15. Taussig, L. M., Chairman. Standardization of lung function testing

in children. Proceedings and Recommendations of the GAP

Conference Committee, Cystic Fibrosis Foundation. J. Pediatrics

97: 668-676 (1980).

16. Kanner, R. E., Schenker, M. B., Munoz, A., and Speizer, F. E.

Spirometry in children. Am. Rev. Respir. Dis. 127: 720-724 (1983).

17. Hargreave, F E., Sterk, P J., Ramsdale, E. H., Dolovich, J., and

Zamel, N. Inhalation challenge tests and airway responsiveness in

man. Chest 87: 202S-206S (1985).

18. Allen, G. A., Turner, W. A., Wolfson, J. M. and Spengler, J. D.

Description of a continuous sulfuric acid/sulfate monitor.

Presentation at the Fourth Annual National Symposium on Recent

Advances in Pollutant Monitoring of Ambient Air and Stationary

Sources, Raleigh, North Carolina, May 1984.

19. Koutrakis, P., Wolfson, J. M., and Spengler, J. D. An improved

method for measuring aerosol strong acidity: Results from a 9

month study in St. Louis, MO, and Kingston, TN. Atmos. Environ.

22: 157-162 (1988).

20. Spengler, J. O., Allen, G., and Koutrakis, P Exposures to Acidic

Aerosols and Gases during the C. A. R. E. S. Study in southwestern

Ontario. Final Report to National Health and Welfare, Harvard

School of Public Health, Boston, MA.

21. Thurston, G. D., and Waldman, J. M. Acid aerosol episodes in

Toronto, Ontario. Preprint. Air Pollution Control Association, 80th

Annual Meeting, New York, NY, June 21-26, 1987.

22. Ontario Ministry of the Environment. 1980 Hamilton Air Quality.

Report of Technical Support Section, West Central Region, July

1981.

23. Koenig, J. Q., Pierson, W. E., and Horikie, M. The effect of inhaled

sulfuric acid on pulmonary function in adolescent asthmatics. Am.

Rev. Respir. Dis. 128: 221-225 (1983).

24. Koenig, J. Q., Covert, D. S., and Pierson, W. E. Effects of inhalation

of acidic compounds on pulmonary function in allergic adolescent

subjects. Environ. Health Perspect. 79: 173-177 (1988).

25. Utell, M. J. Effects of inhaled acid aerosols on lung mechanics: An

analysis of human exposure studies. Environ. Health Perspect. 63:

39-44 (1985).

26. Raizenne, M. E., Hargreaves, F, Sears, M., Spengler, J. D., Stern,

B., and Burnett, R. T. Exercise and lung function responses during

an air pollution episode in young females with airway

hyperresponsiveness to methacholine (abstract). Am. Rev. Respir.

Dis. 135: A343 (1987).

27. Weiss, S. T, Tager, I. B., Weiss, J. W., Munoz, A., Speizer, E E., and

Ingram, R. H. Airways responsiveness in a population sample of

adults and children. Am. Rev. Respir. Dis. 129: 898-902 (1984).

28. Utell, M. J. Measurements of central and peripheral pulmonary

function to assess responses to air pollutants: An overview. In:

Inhalation Toxicology of Air Pollution: Clinical Research for

Regulatory Policy (R. Frank, J. J. O'Neil, M. J. Utell, J. D. Hackney,

J. Van Ryzin, and P E. Brubaker, Eds.), American Society for

Testing and Materials, Philadelphia, 1985, pp. 43-52.