National vehicle emissions policies and practices and declining US carbon monoxide-related mortality.
BACKGROUND
Carbon monoxide (CO) has been reported to contribute to more than 2000 poisoning deaths per year in the United States.


OBJECTIVE
To evaluate the influence of national vehicle emissions policies and practices on CO-related mortality and to describe 31 years (1968-1998) of CO-related deaths in the United States.


METHODS
Longitudinal trend analysis using computerized death data from the Centers for Disease Control and Prevention, US Census Bureau population data, and annual CO emissions estimates for light-duty vehicles provided by the US Environmental Protection Agency.


METHODS
All deaths in the US for which non-fire-related CO poisoning was an underlying or contributing condition, classified by intent and mechanism of death. Negative binomial regression was used to incorporate every year of data into estimated percentage changes in CO emissions and mortality rates over time.


RESULTS
During 1968-1998, CO-related mortality rates in the United States declined from 20.2 deaths to 8.8 deaths per 1 million person-years (an estimated decline of 57.8%; 95% confidence interval [CI], -62.4% to -52.6%). Following the introduction of the catalytic converter to automobiles in 1975, CO emissions from automobiles decreased by an estimated 76.3% of 1975 levels (95% CI, -82.0% to -70.4%) and unintentional motor vehicle-related CO death rates declined from 4.0 to 0.9 deaths per 1 million person-years (an estimated decline of 81.3%; 95% CI, -84.8% to -77.0%). Rates of motor vehicle-related CO suicides declined from 10.0 to 4.9 deaths per 1 million person-years (an estimated decline of 43.3%; 95% CI, -57.5% to -24.3%). During 1975-1996, an annual decrease of 10 g/mile of estimated CO emissions from automobiles was associated with a 21.3% decrease (95% CI, -24.2% to -18.4%) in the annual unintentional motor vehicle-related CO death rate and a 5.9% decrease (95%CI, -10.0% to -1.8%) in the annual rate of motor vehicle-related CO suicides.


CONCLUSIONS
If rates of unintentional CO-related deaths had remained at pre-1975 levels, an estimated additional 11 700 motor vehicle-related CO poisoning deaths might have occurred by 1998. This decline in death rates appears to be a public health benefit associated with the enforcement of standards set by the 1970 Clean Air Act.
Air Pollution and Respiratory Health Branch, National Center for Environmental Health, Centers for Disease Control and Prevention, 1600 Clifton Rd NE, MS E-17, Atlanta, GA 30333, USA. zud9@cdc.gov
Joshua A
JA
Mott
Mitchell I
MI
Wolfe
Clinton J
CJ
Alverson
Steven C
SC
Macdonald
Chad R
CR
Bailey
Lauren B
LB
Ball
Jeanne E
JE
Moorman
Joseph H
JH
Somers
David M
DM
Mannino
Stephen C
SC
Redd
D000059:Accidents / Q000706:statistics & numerical data; D000293:Adolescent; D000328:Adult; D000368:Aged; D000393:Air Pollutants / Q000592:standards*; D002249:Carbon Monoxide Poisoning / Q000453:epidemiology / Q000401:mortality* / Q000517:prevention & control; D005260:Female; D006708:Homicide / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D013405:Suicide / Q000706:statistics & numerical data; D014481:United States / Q000453:epidemiology; D001335:Vehicle Emissions / Q000331:legislation & jurisprudence / Q000506:poisoning / Q000517:prevention & control
D000393:Air Pollutants; D001335:Vehicle Emissions