Exposure to secondhand smoke harms children more than adults

  Article date: 2003/02/05,CDC Study Measures Traces Of 116 Chemicals In The Body

Efforts to clear the air of tobacco smoke have dramatically reduced levels of the byproduct cotinine in the bodies of nonsmokers according to a new report, the Second National Report on Human Exposure to Environmental Chemicals by the Centers for Disease Control.

But children and blacks showed far less improvement. Children had twice the levels measured in adults, and blacks had higher levels than non-Hispanic whites or Mexican Americans.

Experts at the Centers for Disease Control tested blood and urine samples for a total of 116 chemicals, including dioxin, PCBs, some organophosphates, and DDT – some of which have a possible role in causing cancer.

Among children ages 1 to 5, the percentage with elevated blood lead levels dropped from 4.4% to 2.2% between the early 1990s and 1999-2000. And while lead exposure is not known to be a cancer risk, this drop shows the success of public health efforts to protect Americans from toxic chemicals in the environment.

Toxic is how many Americans came to think of environmental tobacco smoke (ETS) during the 1990s when no-smoking signs multiplied in some cities and states. ETS has been linked to lung cancer, heart disease, and respiratory diseases in healthy nonsmokers.

"I think the good news is policies in workplaces, airports, and restaurants are protecting non-smoking adults," explained Elizabeth Ward, Ph.D., Director of Surveillance Research for ACS after reviewing the report. "But children are likely being exposed at home from parents and other caregivers," she added.

Cotinine levels in adults were 75% lower in 1999-2000 than in a study of the same population in 1991-9994. Cotinine is a metabolite (smaller element) of nicotine, the chemical that makes tobacco so addictive. Cotinine itself is not harmful, but acts as a barometer of a person’s exposure to the entire toxic stew of chemicals in tobacco smoke.

By The Numbers:

Cotine levels and therefore, exposure to secondhand smoke dropped as follows from the early 1990s to 1999-2000:

* Adults: Down 75%
* Adolescents: Down 55%
* Children: Down 58%

Note: Blacks of all ages combined had cotinine levels more than twice those for Mexican Americans and non-Hispanic whites.

Blood and urine samples were collected from about 2,500 participants in CDC’s National Health and Nutrition Examination Survey (NHANES)—an ongoing national health survey of the U.S. population.

Have More People Quit Smoking?

Although nonsmokers appear to have more protection against secondhand smoke, Ward says the big picture of cancer and death caused by tobacco is not so encouraging. "If you look at people who are smoking, those numbers haven’t gone down that much."

"There needs to be more medical support to help people stop smoking. When an employer puts a smoke-free policy in place, that company should combine it with a smoking cessation program to help employees quit."
Mexican Americans Have Higher Exposure To DDT

The US government banned use of the pesticide DDT (dichlorodiphenyltrichloroethane) in 1973, but traces can still be found in Americans by measuring the metabolite DDE. The new report shows levels have dropped since before 1990, but serum DDE levels are three times higher among Mexican Americans than whites or blacks. Also, DDE levels are clearly measurable in people aged 12-19 years who were born after DDT was banned in the US. Continued exposure may be from DDT/DDE in the environment or DDT residues in food.

Levels of dioxin, as well as the dioxin-like furans, and polycholorinated biphenyls (PCBs) were lower than lab methods could measure for most of the population tested.

Scientists have developed new ways to accurately measure chemicals in very tiny amounts, and the new CDC report includes exposure information on 89 chemicals never measured in a sample of the US population before. This report will establish baseline levels of these chemicals for most Americans. Researchers who investigate an unusual cluster of cancer cases or other illness will more readily be able to identify an abnormally high chemical exposure.

"This report is by far the most extensive assessment ever of exposure of the U.S. population to environmental chemicals,” said CDC Director Dr. Julie Gerberding, “This kind of exposure information is essential; it helps us to lay the critical groundwork for future research in ensuring that exposures to chemicals in our environment are not at levels that affect our health.”
Fear In The General Public

According to the report, the chemicals measured include mercury, uranium, cadmium, thallium, and other metals; and substances that have been in the news for a possible link to cancer such as:

Phthalates: Industrial chemicals found in soap, detergent, shampoo, plastic bags, plastic food packaging, garden hoses, children’s toys, raincoats, and other consumer products.

Organochlorine pesticides: Such as DDT and its metabolite DDE.

Herbicides: Including atrazine, which is widely used on corn crops in the US.

Polycyclic aromatic hydrocarbons (PAH) : Produced by tobacco smoking, air pollution, and grilling, smoking or roasting food.

Carbamate insecticides: Widely used against insects, fungi, and weeds in agriculture and home lawns and gardens.

Organophosphate pesticides: Used on agricultural crops, in residential and commercial buildings, plants, lawns, and for mosquito control.

Specific organophosphate pesticides: Malathion and chlorpyrifos, which is used against ants and other insects under the brand name Dursban.

Phytoestrogens: Substances in some plants that act like estrogens in people.

Ward says people shouldn’t be alarmed by these early measurements of many chemicals. "There is a fear in the general public that exposure to environmental chemicals is going up and that cancer is increasing too, but for the majority of cancer types, incidence is going down."

"Often the public has a higher level of concern about environmental chemicals than is warranted by the evidence, while the evidence that tobacco use causes cancer is very, very strong. Lifestyle risk factors account for a high proportion of cancer cases and cancer deaths," she explained.

Looking at the big picture, Ward points out that environment chemicals are important for many reasons, not just as possible causes of cancer but also because of their potential to affect the nervous or reproductive systems of humans. Therefore, it’s extremely important to monitor the levels of public exposure to chemicals in the environment, and this report is a huge step forward in that effort.

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