Explanation
NIOSH took air samples of carbon monoxide (CO) for a health study on the effects of CO exposure.
ppm: "ppm" means "parts per million." It is a measure of the concentration of a substance in air. For example, 1 ppm of CO means 1 "part" of CO for every one million "parts" of air.
Average level over shift: the concentration of CO averaged over the work shift.
Range: the lowest and the highest concentration of CO for each shift The range is shown for three measurements: 1) the average over the shift, 2) the average over 15 minutes, and 3) the average peak.
Highest 15-minute average: the average of all the highest 15-minute concentrations recorded during each shift.
Average peak: "peak" means the highest concentration recorded for an air sample. The average peak is the average of all the peaks recorded over each shift.
What Does This Mean?
The Occupational Safety and Health Administration (OSHA) has two permissible exposure limits (PELs) for CO exposure. Exposures may not be over 35 ppm averaged over 8 hours and may never be over 200 ppm.
NIOSH's recommendations are the same as OSHA's legal standard.
OSHA does not have legal authority over the PANY & NJ because it is a state agency, but PANY & NJ voluntarily complies with OSHA regulations.
One of the samples was higher than the OSHA PEL for peaks — 229 ppm. We don't know if this represented a routine exposure.
One of the samples was higher than the OSHA PEL for peaks — 372 ppm. We don't know if this represented a routine exposure.
Motor vehicle exhaust contains CO. CO exposures to toll collectors have decreased over the years as vehicle emissions have decreased and ventilation has increased. PANY & NJ varies the air ventilation in the tunnels depending on traffic flow.
Currently, there are no generally recognized health effects from breathing CO at the levels seen in the survey. The first sign of CO poisoning from exposure to higher levels (over 100 ppm) is usually a headache.
However, there is concern that the higher CO levels present in tunnels in the past may have caused more serious health effects. A previous NIOSH study found deaths from heart disease a third higher than expected in tunnel officers.
Any Questions?
If you have any questions about the exposure survey, call NIOSH's toll-free number: 1-800-356-4674.
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES • Public Health Service
Centers for Disease Control • National Institute for Occupational Safely and Health
Cincinnati, Ohio 45226
For more information, call the NIOSH toll-free number: 1-800-356-4674.