Monday, 31 October 2011
Carbon Monoxide Kills Newsletter Launched!
Introduction by Dr. David G. Penney
We are all aware that carbon monoxide is a deadly poison at high concentrations and its lethality is the result of impaired oxygen delivery to cells as it binds to hemoglobin in the blood. Recent research suggests that CO has health effects in humans at low and even ultra-low concentrations, and that these effects are mediated through previously unknown mechanisms not involving hypoxia. It may well be that what we knew before 2000, is at best, only a fraction of the story regarding CO toxicology.
A comprehensive report “Selected Pollutants: WHO Guidelines for Indoor Air Quality” became available to the public, December 15, 2010. This report, book length, can be purchased from WHO, Bonn, and elsewhere. The chapter on CO was deveIoped by a committee of six scientists, three Americans, two Italians and one French woman. I wrote the initial draft of a substantial portion of that chapter.
This report is revolutionary in several respects: 1) The new 24-hour guideline for CO exposure is 7.0 mg/m3, or about 6.5 ppm. Prior to this, no change in safety guidelines had been made by national or international agencies in more than 25-years. This decision was based on new epidemiologic studies of data from thousands, 10s or even 100s of thousands of people. These studies imply that CO is even more toxic to humans than previously believed in the past based on limited numbers of studies using relatively small sample sizes. The new epidemiologic studies support long held beliefs that chronic CO exposure at low or even ultra-low levels can produce severe and lasting health effects. 2) That there may be NO safe lower limit (no NOAEL) for CO exposure – as has been known for ionizing radiation for decades. 3) That carboxyhemoglobin (COHb) is a poor metric for the severity of CO poisoning, especially for chronic CO poisoning.
During mid-2010, I gave testimony in a Massachusetts (USA) court in a case where defense challenged me to show evidence of neurological effects at CO concentrations of 9 ppm (long-standing EPA & WHO outside air guidelines) or less. Based on the new study data referenced above, the judge ruled against defense and for my opinions. This, combined with our new understanding of how CO damages the body independent of COHb and hypoxia, and at far lower low CO exposure levels than hypoxia can do (i.e. oxidative & immunologic mechanisms), opens a new window to our understanding of the extremely toxic nature of CO and its deleterious effects on human health.
David G. Penney, Ph.D., Professor of Physiology (retired)