Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Trends in exposure to environmental tobacco smoke in schoolchildren in England from 1988 to 1998 by parental smoking habits, as shown by salivary cotinine concentrations in non-smoking children. Values are geometric means (95% confidence intervals)
