Secondhand Smoke

Children who are exposed to secondhand smoke have an increased probability of experiencing adverse health effects such as infections of the lower respiratory tract, bronchitis, pneumonia, middle ear disease, sudden infant death syndrome (SIDS), and respiratory symptoms.60 Secondhand smoke also can play a role in the development and exacerbation of asthma.60 The U.S. Surgeon General has determined that there is no risk-free level of exposure to secondhand smoke.60 Cotinine, a breakdown product of nicotine, is a marker for recent (previous 1–2 days) exposure to secondhand smoke in nonsmokers.

Indicator PHY2.A: Percentage of children ages 4–11 with specified blood cotinine levels, selected years 1988–2018
Indicator PHY2.A: Percentage of children ages 4–11 with specified blood cotinine levels, selected years 1988–2018

NOTE: Cotinine levels are reported for nonsmoking children only. "Any detectable cotinine" indicates blood cotinine levels at or above 0.05 nanograms per milliliter (ng/mL), the level of cotinine that could be detected in blood in 1988–1994. The average (geometric mean) blood cotinine level in children living in homes in which someone smoked was 1.0 ng/mL in 1988–1994.61

SOURCE: National Center for Health Statistics, National Health and Nutrition Examination Survey.

Indicator PHY2.B: Percentage of children ages 4–11 with any detectable blood cotinine level by race and Hispanic origin and poverty status, 2017–2018
Indicator PHY2.B: Percentage of children ages 4–11 with any detectable blood cotinine level by race and Hispanic origin and poverty status, 2017–2018

NOTE: NH = non-Hispanic origin. Cotinine levels are reported for nonsmoking children only. "Any detectable blood cotinine" indicates blood cotinine levels at or above 0.05 nanograms per milliliter (ng/mL), the detectable level of cotinine in the blood in 1988–1994. Beginning in 2007, the National Health and Nutrition Examination Survey allows the reporting of both total Hispanics and Mexican Americans; however, estimates reported here are for Mexican Americans to be consistent with earlier years. Persons of Mexican American origin may be of any race.

SOURCE: National Center for Health Statistics, National Health and Nutrition Examination Survey.



  • In 2017–2018, 57% of Black, non-Hispanic children ages 4–11 had detectable blood cotinine levels compared with 39% of White, non-Hispanic children and 22% of Mexican American children.
  • About 55% of children ages 4–11 living in poverty had detectable blood cotinine levels in 2017–2018 compared with 31% of children living above the poverty level.
  • The percentage of children ages 4–11 with detectable blood cotinine levels [at or above 0.05 nanograms per milliliter (ng/mL)] decreased from 85% in 1988–1994 to 36% in 2017–2018.












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60 U.S. Department of Health and Human Services. (2006). The health consequences of involuntary exposure to tobacco smoke: A report of the Surgeon General. Centers for Disease Control and Prevention, Coordinating Center for Health Promotion, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health.

61 Mannino, D. M., Caraballo, R., Benowitz, N., & Repace, J. (2001). Predictors of cotinine levels in U.S. children: Data from the Third National Health and Nutrition Examination Survey. CHEST, 120, 718–724.

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