As is well-known, carbon monoxide (CO) is a toxic, odorless, colorless gas capable of producing discomfort, illness, mental and physical disability and/or death if present in inhaled air, gas or smoke in sufficiently high concentrations. Combustion of many kinds such as occurs in coal and oil fires, gas flames, internal combustion engines, and burning tobacco, in particular, are common sources of CO. Marshes also generate CO.
Even non-smokers are frequently exposed to potentially excessive quantities of carbon monoxide since carbon monoxide is a substantial air pollutant produced by automobiles, internal and external combustion engines, in many industrial processes, and by neighboring smokers. Thus, guards and workers in automobile tunnels, or passengers in automobiles may be exposed to excessive quantities of carbon monoxide.
As an illustration of the danger presented by carbon monoxide in air, studies have shown that where the product of hours of exposure and parts of carbon monoxide per 10,000 parts of air equal 15, a danger to life is present. It therefore would be highly desirable that effective means be found for absorbing carbon monoxide either at the point where generated or from air to be inhaled by individuals.
Hemoglobin, the term as used herein designating ferrous hemoglobin or oxyhemoglobin, is an attractive possibility for use toward such ends but has not been available due to the fact that when it is no longer within the erothrocyte and is exposed to oxygen of the air it forms methemoglobin which is inactive toward carbon monoxide. Further, the equivalent weight of hemoglobin is high, making it necessary that relatively large quantities of the material be used for absorption of carbon monoxide. The molecular weight of hemoglobin is about 66,000 and each hemoglobin molecule contains four iron atoms, active in absorbing carbon monoxide, so that the equivalent weight of hemoglobin relative to absorption of carbon monoxide is about 16,500. In contrast, the molecular weight of each heme moiety which contains an atom of iron is approximately 600. Since it is this portion of the hemoglobin molecule which is responsible for the absorption of carbon monoxide by the formation of a stable complex, it would obviously be desirable to eliminate, in so far as is possible, those portions of the hemoglobin molecule which are inactive with respect to absorption of carbon monoxide.