NCHS Data Brief ■ No. 126 ■ August 2013

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Center for Health Statistics

Environmental Tobacco Smoke Exposure in Children 

Aged 3‒19 Years With and Without Asthma in the

United States, 1999‒2010

Kenneth B. Quinto, M.D., M.P.H; Brian K. Kit, M.D., M.P.H.; Susan L. Lukacs, D.O., M.S.P.H.; 

and Lara J. Akinbami, M.D.

Environmental tobacco smoke (ETS) has harmful effects on children’s 

respiratory health and has been linked to higher risk of middle ear infections, 

bronchitis and pneumonia, coughing and wheezing, worse lung function, and 

asthma development (1). Children with asthma whose parents smoke have 

more severe symptoms and more frequent exacerbations (1). National asthma 

guidelines recommend ETS exposure be minimized among persons with 

asthma (2). ETS exposure in children with and without asthma has not been 

directly compared in a national sample of the U.S. population. This report 

presents trends in ETS exposure in children with and without asthma from 

1999 to 2010, and describes differences by sex, race and ethnicity, income, and 

age group in 2007–2010.

Keywords: National Health and Nutrition Examination Survey • childhood 

asthma

The percentage of children aged 3‒19 years without asthma 

exposed to ETS decreased from 1999 to 2010, while the 

percentage with asthma exposed to ETS did not change.

Key findings

Data from the National 

Health and Nutrition 

Examination Survey, 

1999‒2010

•	 From 1999 to 2010, 

the percentage of children 

without asthma exposed to 

environmental tobacco smoke 

(ETS) decreased from 57.3% 

to 44.2%, while children with 

asthma showed no change, 

with 57.9% exposed to ETS in 

1999‒2002	and	54.0%	exposed	

in	2007‒2010.

•	 In	2007‒2010,	a	higher	

percentage of children with 

asthma were exposed to ETS 

than children without asthma.

•	 In	2007‒2010,	children	with	

asthma were more likely to be 

exposed to ETS than children 

without asthma, if they were 

girls, Mexican American, aged 

6‒11	years,	or	had	family	

income below 350% of the 

federal poverty guidelines.
NCHS Data Brief ■ No. 126 ■ August 2013

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From 1999 to 2010, the percentage of children without asthma exposed to ETS decreased from 

57.3% to 44.2%, while the percentage of exposed children with asthma showed no decline; 57.9% 

in	1999‒2002	and	54.0%	in	2007‒2010	(Figure 1). There was no difference in ETS exposure 

between children with asthma and children without asthma in 1999–2002 and 2003–2006. The 

percentage of children exposed to ETS was higher among children with asthma than those 

without asthma in 2007–2010.

In 2007‒2010, the percentage of ETS exposure was higher in girls with 

asthma than in girls without asthma.

In girls with asthma, 57.6% experienced ETS exposure, while 43.6% of girls without asthma 

had ETS exposure. No difference was seen in the percentage exposed to ETS between boys with 

asthma (50.8%) and without asthma (44.7%) (Figure 2).
NCHS Data Brief ■ No. 126 ■ August 2013

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A higher percentage of Mexican-American children with asthma had ETS 

exposure than Mexican-American children without asthma.

The percentage exposed to ETS was higher for Mexican-American children with asthma (38.2%) 

than those without asthma (27.4%) (Figure 3). No other differences were seen between children 

with and without asthma by race and ethnicity. 
NCHS Data Brief ■ No. 126 ■ August 2013

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Among children with family income below 350% of the federal poverty 

guidelines, those with asthma experienced higher prevalence of ETS 

exposure than those without asthma.

Among children in families with income below 185% of the federal poverty guidelines, children 

with asthma had higher prevalence of ETS exposure than children without asthma. The same 

was also true among children from families with income between 185% and 350% of the federal 

poverty guidelines. No difference in ETS exposure was seen between children with and without 

asthma from higher-income families (350% of the federal poverty guidelines and above) (Figure 4). 
NCHS Data Brief ■ No. 126 ■ August 2013

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Children aged 6‒11 with asthma experienced a higher percentage of ETS 

exposure than children without asthma.

Among	children	aged	6‒11,	those	with	asthma	had	a	higher	percentage	of	ETS	exposure	(58.8%)	

than those without asthma (44.7%) (Figure 5). No difference was seen in ETS exposure between 

children with and without asthma in the other age groups. 

Summary

The National Asthma Education and Prevention Program Guidelines for Diagnosis and 

Management of Asthma recommend that people with asthma avoid tobacco smoke exposure (2). 

Asthma	is	common	among	children	in	the	United	States.	In	2007‒2010,	1	child	in	10	had	asthma.	

However,	while	ETS	exposure	among	children	aged	3‒19	without	asthma	decreased	from	57.3%	

to	44.2%	from	1999‒2010,	there	was	no	change	during	this	period	in	the	percentage	of	children	

with asthma who were exposed to ETS. As a result, ETS exposure among children with asthma 

was	higher	(54.0%)	than	for	those	without	asthma	(44.2%)	in	2007‒2010.	Among	demographic	

subgroups of children with asthma, girls, Mexican-American children, those with family income 

below	350%	of	the	federal	poverty	guidelines,	and	children	aged	6‒11	experienced	higher	

ETS exposure than their counterparts without asthma. More in-depth analysis may provide an 

explanation for these differences among these subgroups.

Definitions

Child with asthma:	Based	on	an	affirmative	response	to	both	the	following	questions:	“Has	a	

doctor	or	other	health	professional	ever	told	you	that	[sample	child]	has	asthma?”	and	“Does	

[sample child] still have asthma?”
NCHS Data Brief ■ No. 126 ■ August 2013

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Environmental tobacco smoke (ETS) exposure: Only children who were classified as nonsmokers

were included in the analysis. Smokers were defined as respondents aged 12–19 who answered

“yes” to the question of use of tobacco products in the last 5 days or whose serum cotinine

measurement was greater than 10 ng/mL. Serum cotinine is a breakdown product of nicotine. 

Among nonsmokers, serum cotinine measurements greater than or equal to 0.05 ng/mL and less 

than or equal to 10 ng/mL were considered to indicate recent exposure to ETS, and those less than 

0.05 ng/mL were considered to indicate no exposure (3,4). 

Family income to poverty ratio (FIPR): An index representing the ratio of family income to 

the federal poverty threshold based on family size. The U.S. Department of Health and Human 

Services’ poverty guidelines were used as the poverty measure to calculate this index (5). Income 

eligibility for participation in some federal programs, including reduced-price lunches during the 

study period, is 185% (FIPR less than 1.85) of the poverty guidelines (6). 

Data source and methods

National Health and Nutrition Examination Survey (NHANES) data were used for these analyses. 

NHANES is conducted by the Centers for Disease Control and Prevention’s National Center for 

Health Statistics to assess the health and nutritional status of the civilian noninstitutionalized 

U.S. population. The survey consists of both an in-home interview and a standardized physical 

examination at a mobile examination center (MEC). The data for this report were collected from 

in-home interviews and an in-person standardized physical examination conducted at a MEC 

where participants had blood samples taken to perform various testing, including serum cotinine 

measurement. Serum cotinine was measured only in participants aged 3 years and over. Between 

1999‒2000 and 2009‒2010, the response rate to the survey ranged from 78.4% in 2007‒2008 to

84.0% in 2001‒2002 (7). 

The sample design includes oversampling to obtain reliable estimates of health and nutritional 

measures for population subgroups. In 2007‒2010, NHANES oversampled low-income persons,

non-Hispanic black persons, and Hispanic persons. Data were analyzed using sample weights to 

account for differential probabilities of selection, nonresponse, and noncoverage. The standard 

errors of the percentages were estimated using Taylor series linearization, a method that accounts 

for the complex sampling design of NHANES. 

Differences between groups were evaluated using a t statistic at the p < 0.05 significance level

with the appropriate degrees of freedom. Differences between percentages were evaluated using 

two-sided significance tests at the 0.05 level. To test for linear trends between ETS exposure

and children with and without asthma over time, the null hypothesis of nonlinear trend was 

examined using univariate logistic regression. Terms such as “higher than” and “less than”

indicate statistically significant differences. Terms such as “similar” and “no difference” indicate

that the statistics being compared were not significantly different. Lack of comment regarding

the difference between any two statistics does not necessarily suggest that the difference was 

tested and found to be not significant. Statistical analyses were conducted using SAS System

for Windows version 9.3 (SAS Institute Inc., Cary, N.C.) and SUDAAN version 11.0 (RTI 

International, Research Triangle Park, N.C.).
NCHS Data Brief ■ No. 126 ■ August 2013

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About the authors

Kenneth B. Quinto is with the Centers for Disease Control and Prevention’s (CDC) Epidemic 

Intelligence Service and the National Center for Health Statistics, Office of Analysis and

Epidemiology. Brian K. Kit is with CDC’s National Center for Health Statistics, Division of 

Health and Nutrition Examination Surveys. Susan L. Lukacs and Lara J. Akinbami are with 

CDC’s National Center for Health Statistics, Office of Analysis and Epidemiology.

References

1. U.S. Department of Health and Human Services. The health consequences of involuntary 

exposure to tobacco smoke: A report of the Surgeon General. Rockville, MD: Public Health 

Service. 2006.

2. National Asthma Education and Prevention Program. Expert panel report 3: Guidelines for the 

diagnosis and management of asthma. Bethesda, MD: National Heart, Lung, and Blood Institute. 

2007.

3. Pirkle JL, Flegal KM, Bernert JT, Brody DJ, Etzel RA, Maurer KR. Exposure of the US 

population to environmental tobacco smoke: The Third National Health and Nutrition Examination 

Survey, 1988 to 1991. JAMA 275(16):1233–40. 1996.

4. Centers for Disease Control and Prevention. Disparities in secondhand smoke exposure—

United States, 1988–1994 and 1999–2004. MMWR 57(27):744–7. 2008.

5. U.S. Department of Health and Human Services. Poverty guidelines, research, and 

measurement. 2013. Available from: http://aspe.hhs.gov/poverty/index.cfm [Accessed March 11, 

2013].

6. U.S. Department of Agriculture. Child nutrition programs—Income eligibility guidelines. Fed 

Regist 74(58):13410–2. 2009. Available from: http://www.fns.usda.gov/cnd/Governance/notices/

iegs/IEGs09-10.pdf [Accessed March 11, 2013].

7. National Health and Nutrition Examination Survey. NHANES response rates and CPS totals. 

1999–2010 response rates. Available from: http://www.cdc.gov/nchs/nhanes/response_rates_

CPS.htm [Accessed May 28, 2013].
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Suggested citation

Quinto KB, Kit BK, Lukacs SL, Akinbami 

LJ. Environmental tobacco smoke exposure 

in children aged 3‒19 years with and

without asthma in the United States, 

1999‒2010. NCHS data brief, no 126.

Hyattsville, MD: National Center for Health 

Statistics. 2013.

Copyright information

All material appearing in this report is in 

the public domain and may be reproduced 

or copied without permission; citation as to 

source, however, is appreciated.

National Center for Health 

Statistics

Charles J. Rothwell, M.S., Acting Director

Jennifer H. Madans, Ph.D., Associate 

Director for Science

Office of Analysis and Epidemiology

Irma E. Arispe, Ph.D., Director