PROSPECTIVE STUDY OF AIR POLLUTION AND BRONCHITIC 

SYMPTOMS IN CHILDREN WITH ASTHMA

ONLINE DATA SUPPLEMENT

Rob McConnell, M.D.

Kiros Berhane, Ph.D.

Frank Gilliland, M.D., Ph.D.

Jassy Molitor

 Duncan Thomas

Fred Lurmann

Edward Avol, M.S.

W. James Gauderman, Ph.D.

John M. Peters, M.D.
RESULTS

Table E1: Pearson correlation coefficients of 4-year average pollutant concentrations across study communities 

(N=12)

NO2 O3 PM10 PM2.5 PM10-2.5

Inorganic 

acid

Organic

acid EC OC

NO2 1

O3 -0.17 1

PM10 0.63* 0.20 1

PM2.5 0.75† 0.21 0.96† 1

PM10-2.5 0.43 0.18 0.94† 0.82† 1

Inorganic acid 0.84† 0.36 0.72† 0.83† 0.51 1

Organic acid 0.83† 0.33 0.83† 0.88† 0.69* 0.94† 1

EC 0.92† 0.01 0.86† 0.92† 0.70* 0.88† 0.90† 1

OC 0.58* 0.18 0.97† 0.90† 0.95† 0.64* 0.81† 0.81† 1

*P < .05; † P < .01
The between–community effect estimates for the pollutants examined were, in general, 

not significant in the presence of other pollutants in two pollutant models (see Table E2). 

The effect estimates for NO2 (? = 0.017/ppb) and for EC (? = 0.441/μg/m3) in single 

pollutant models were markedly attenuated in models with PM2.5. The effect of NO2 was 

modestly reduced when adjusted for PM10, EC, or OC. The effect of PM2.5 (? = 

0.026/μg/m3) was markedly reduced, when adjusted for NO2. No pollutant had a 

consistent significant association with symptoms in models adjusted for other pollutants.

Table E2: Two pollutants models of between-community effects (4-year average 

concentrations; N=12) among children with asthma* 

Main

Pollutant

 Adjustment pollutants

NO2 O3 PM10 PM2.5 PM10-2.5

Inorganic 

acid

Organic

acid EC OC

NO2 0.017† 0.016† 0.014 0.009 0.017† 0.020 0.017 0.014 0.014

O3 -0.003 -0.006 -0.009 -0.010 -0.007 -0.012 -0.011 -0.006 -0.008

PM10 0.004 0.013 0.011 -0.027 0.043† 0.009 0.006 -0.001 0.010

PM2.5 0.016 0.029‡ 0.069 0.026† 0.043† 0.036 0.034 0.025 0.037

PM10-2.5 0.000 0.016 -0.069 -0.027 0.013 0.003 -0.005 -0.011 -0.070

Inorganic -0.037 0.137† 0.035 -0.069 0.089 0.098 -0.044 -0.073 0.044

acid

Organic -0.001 0.091† 0.039 -0.035 0.078 0.094 0.069 -0.027 0.050

acid

EC 0.097 0.443† 0.450 0.018 0.557 0.658 0.567 0.441† 0.389

OC 0.020 0.059 0.004 -0.043 0.213† 0.043 0.021 0.004 0.054

*Each row gives estimates (beta) for the indicated pollutant, adjusted for age, maternal and child’s smoking history, 

sex, and race, the within-community effect of that pollutant and for both the between- and within-community effect 

of the adjustment pollutant listed at the top of each column. The estimate for each pollutant in a single pollutant 

model is presented along the diagonal (in bold). Estimates are expressed per ppb for NO2, O3, acid; per ?g/m3 for 

PM, elemental and organic carbon.

†P < .05; ‡P < .01
Figure E1

Figure E1: Odds ratios for the within-community effects of NO2 and of organic carbon, 

adjusted for each of the other pollutants examined.

 A: Risk of Bronchitic Symptoms as a Function

 of Yearly Deviation in NO2

0.9

1.0

1.1

1.2

1.3

1.4

1.5

NO2+

O3(10-6)

PM10

PM2.5

PM10-25

I ACID

O ACID

EC

OC

Adjustment Air Pollutants

Odds Ratio* / ppb

B: Risk of Bronchitic Symptoms as a Function of Yearly 

Deviation in OC

0.5

1.0

1.5

2.0

2.5

3.0

3.5

OC+

NO2

O3(10-6)

PM10

PM2.5

PM10-25

I ACID

O ACID

EC

Adjustment Air Pollutants

Odds Ratio* / (mcg / m

3

)

*All odds ratios were adjusted for age, maternal and child’s smoking history, sex, and 

race, and for the between-community effect of the pollutant indicated. 

+NO2+ and OC+ indicate the within-community odds ratio in a single pollutant model, 

adjusted only for the between-community effects of NO2 (A) and OC (B) and for 

personal covariates. All other odds ratios are also for NO2 (A), or for OC (B), but 

adjusted in addition for both within- and between-community effects of the adjustment 

pollutant indicated.