Carbon monoxide exposure and carboxyhemoglobin.

Given recent survey data showing that physicians ask their patients about carbon monoxide less frequently than any other common environmental health hazard (Kilpatrick et al. 2002), I welcome your effort to increase awareness of CO by publishing the case report of Devine et al. (2002) documenting "MRI and Neuropsychological Correlates of Carbon Monoxide Exposure." But why did they include a table purporting to specify "Human responses and approximate ambient CO air levels at various carboxyhemoglobin concentrations" (Table 2; Devine et al. 2002)?

Devine et al. (2002) reported being unable to obtain any CO exposure data and did not even mention their patient's carboxyhemoglobin (HbCO) level, which they apparently saw no need to measure or even report. In fact, Devine et al. gave several reasons for not relying on HbCO, including (quoting Myers et al. 1998) that it is "of little value in diagnosing either acute or chronic CO poisoning."

Their Table 2 (Devine et al. 2002) is misleading because it does not specify the duration of CO exposure, air temperature, altitude, the initial HbCO level of those exposed, the level of physical exertion, smoking status, blood alcohol level, breathing rate, age, or any of the many other variables known to significantly influence the variety and severity of CO symptoms at any HbCO level.

Most misleading is that the table suggests that no symptoms of any kind--aside from angina in heart patients upon exertion--should be expected under 10% HbCO. EHP is just one of several journals that have recently published large studies of human CO exposure documenting that increases of just 1-2 ppm in average outdoor CO levels--well below those associated with any increase in HbCO--are more significantly associated with increasing asthma prevalence (Guo et al. 1999) and asthma attacks (Yu et al. 2000) than any other atmospheric pollutant including ozone and particulates.

Moreover, although Devine et al. (2002) referenced their Table 2 to "data from O'Donoghue" (O'Dohoghue 1985), from which it was indeed copied, O'Donoghue's version does not cite any actual data but merely four other sources (Ginsberg 1980; Stewart 1975, 1976; Stewart et al. 1970). Although three of these contain similar HbCO tables, they also do not cite any relevant data, just other published sources.

I had to check 14 such references before I found what appears to be the original Table--itself unreferenced--in a typewritten "Report of Investigations" published by the U.S. Bureau of Mines in 1923 (Sayers and Yant 1923), apparently without any external peer review. The table (Sayers and Yant 1923) was qualified with the phrase "in general" and was clearly not based on any actual human data or study. Given that the version published by Devine et al. (2002) is thus without any credible foundation, misleading in its content, and irrelevant to their reported case, I urge them to retract it from their otherwise excellent paper.

The author declares he has no conflict of interest.

REFERENCES

Devine SA, Kirkley SM, Palumbo CL, White RF. MRI and neuropsychological correlates of carbon monoxide exposure: a case report. Environ Health Perspect 110:1051-1055 (2002).

Ginsberg MD. 1980. Carbon monoxide. In: Experimental and Clinical Neurotoxicology (Spencer PS, Schaumburg HH, eds). Baltimore, MD:Williams and Wilkins, 374-394.

Guo YL, Lin YC, Sung FC, Huang SL, Ko YC, Lai JS, et al. 1999. Climate, traffic-related air pollutants, and asthma prevalence in middle-school children in Taiwan. Environ Health Perspect 107:1001-1006 (1999).

Kilpatrick N, Frumkin H, Trowbridge J, Escoffery C, Geller R, Rubin L, et al. 2002. The environmental history in pediatric practice: a study of pediatricians' attitudes, beliefs, and practices. Environ Health Perspect 110:823-827.

Myers RA, DeFazia A, Kelly MP. 1998. Chronic carbon monoxide exposure: a clinical syndrome detected by neuropsychological tests. J Clin Psychol 54(5):555-567.

O'Donoghue JL. 1985. Carbon monoxide, inorganic nitrogenous compounds, and phosphorus. In: Neurotoxicity of Industrial and Commercial Chemicals, Vol 1 (O'Donoghue JL ed). Boca Raton, FL:CRC Press, 193-203.

Sayers RR, Yant WP. 1923. Dangers and Treatment of Carbon Monoxide Poisoning. Reports of Investigations, Serial no. 2476. Washington, DC:Department of the Interior, Bureau of Mines.

Stewart RD. 1975. The effect of carbon monoxide on humans. Annu Rev Pharmacol Toxicol 15:409-423.

--. 1976. The effect of carbon monoxide on humans. J Occup Med 18:304-309.

Stewart RD, Peterson JE, Baretta ED, Bachland RT, Hosko MJ, Herrman AA. 1970. Experimental human exposure to carbon monoxide. Arch Environ Health 21:154-194.

Yu O, Sheppard L, Lumley T, Koenig JQ, Shapiro GG. 2000. Effects of ambient air pollution on symptoms of asthma in Seattle-area children enrolled in the CAMP study. Environ Health Perspect 108:1209-1214.

Albert Donnay

Donnay Environmental Health Engineering

Baltimore, Maryland

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