Environmental Tobacco Smoke Exposure

This page last reviewed  October 11, 2017

Environmental Tobacco Smoke (ETS) exposure in many indoor public places has been on the decline over the past few decades. This decrease has been documented by surveys done by the California Department of Public Health (CDPS), and by biological monitoring conducted by the U.S. Centers for Disease Control (CDC). However, there are still ETS exposures that cause concern, especially for vulnerable populations such as children and the elderly. The home environment, where young children spend most of their time, is the location where they are more likely to experience high exposure. Children may also be exposed to very high concentrations of ETS in vehicles with adult smokers. Similarly, the elderly population whom often suffer from declining health may be exposed by their spouses or younger caregivers. The elderly also face potentially unhealthy exposures to ETS in multi-unit housing complexes. The elderly and others with limited incomes may be the least able to change their living conditions to avoid exposure. 

There are many ways to assess exposure to ETS. In long-term health studies exposure is usually determined with questions about spousal smoking, exposure in the workplace, number of cigarettes smoked, etc. These questionnaires provide only a rough estimate of the length and intensity of exposure. Monitoring for ETS in the ambient environment is usually done with a tracer compound such as nicotine or Respirable Suspended Particles (RSP). RSP measurements estimate the mass of particles less than 10 micrometers in aerodynamic diameter (PM10). These smaller particles are more likely to enter the lung. Most ETS particles are in the "fine" size range of less than 2.5 micrometers (PM2.5). Nicotine is considered the best marker for ETS, given its specificity and well-established methods of monitoring. ARB summarized the scientific literature on indoor ETS monitoring and conducted its own outdoor monitoring study for ETS using nicotine as a marker compound. The results of the literature review and the ARB outdoor study are described in detail in Part A of the 2005 TAC identification report. Key findings from the report can be found in the Report's Executive Summary.

Another method of directly determining exposure to ETS is through biomonitoring. The body metabolizes toxins from the environment and the metabolic products can often be identified by analyzing urine, blood, sputum, etc. The CDC tracks exposure to ETS by measuring cotinine, a metabolite of nicotine, in the blood of nonsmokers. Cotinine measurements are a good indicator of exposure to ETS over the past two to three days, and are sensitive enough to distinguish between an exposed nonsmoker and a smoker. Cotinine analysis has been conducted for nearly two decades on a large sample of the American public. For most of the population, levels of cotinine measured by the CDC have declined by 70 percent since it was first measured. However, the same is not true for children. These measurements show that more than 50 percent of U.S. children are still exposed to ETS, and cotinine levels in children are nearly twice as high as adults. Among the most exposed adult non-smokers, concentrations of cotinine in the blood decreased nearly 40 percent between 1988 and 2002, while the most exposed children showed no significant declines in cotinine concentration.

According to CDPH, smoking prevalence in California has declined by 51.1 percent between 1988 and 2014; this drop represents approciamately 3.3 million fewer adult smokers. However, there are still four million smokers in California, and potentially millions of California children and older Californians exposed to ETS in their own homes. This exposure can lead to serious adverse health outcomes. New cases of asthma and exacerbations of pre-existing asthma can result from ETS exposure. Children's exposure may also cause an increase in the number of medical visits for ear infections, or may result in more respiratory illnesses in general. Elderly adults may be especially susceptible to the cardiovascular effects of ETS, which include heart attacks and chronic heart disease. The Office of Environmental Health Hazard Assessment (OEHHA) estimated the number of deaths and illnesses in California that may be caused by exposure to ETS. These estimates can be found in the Executive Summary of the ARB ETS TAC report.

Links to more information on ETS exposure and health effects are provided below.


ARB Exposure Assessment Proposed Identification of Environmental Tobacco Smoke as a Toxic Air Contaminant; Appendix III, Part A: Exposure Assessment
Environmental Health Perspectives Measurement of ETS Exposure Among Adults with Asthma

Health Effects:

ARB ETS Executive Summary OEHHA listing of Health Effects of ETS exposure
Americans For Nonsmokers' Rights Secondhand Smoke: The Science
Office of Environmental Health Hazard Assesment (OEHHA) Secondhand Smoke and Children's Health
California Department of Public Health: Tobacco Control Branch Smoking During Pregnancy: Health Effects

Contact us if you have any questions regarding CARB's ETS program, or have suggestions or comments on this page.

Robert Krieger: (916) 323-1202