Environmental Medicine: Integrating a Missing Element into Medical Education

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diovascular stress in the patient with coronary heart disease to be dangerous.⁹^–¹²

The elevated COHb level resulting from CH₂Cl₂ exposure has a biological half-life twice that of COHb produced from exposure to CO. This occurs because the absorbed CH₂Cl₂ is released slowly from storage in body tissues and then is metabolized to CO over a protracted period of time. Thus, because it is so sustained following exposure, the cardiovascular stress produced by elevated COHb levels, derived from CH₂Cl₂ metabolism, is greater than that resulting from equally high COHb levels derived from CO. The addition of methanol to paint-remover formulations extends the biologic half-life of COHb derived from CH₂Cl₂ (Figure), further prolonging the period of cardiovascular stress.

The ethical responsibility for informing the public about the potential hazard of CH₂Cl₂ in paint removers lies with the manufacturer who is obliged to market a product that can be used safely. This is the purpose of the label. It should warn the susceptible segment of the population of the CO hazard. The manufacturers of paint removers have been cognizant of the problem since 1972, yet product labels make no mention of CO. Only one manufacturer of paint removers has acted positively. This Racine, Wis, firm has withdrawn its product from the market.

The legal responsibility for protecting the public currently rests with the Consumer Product Safety Commission. It has remained mute, as did the governmental agency originally responsible, the Environmental Protection Agency, when in 1971 the CH₂Cl₂ hazard was formally called to its attention.

The medical responsibility for protecting patients unable to tolerate the cardiovascular stress of elevated COHb levels must rest with the physician until the general public is made aware of the CH₂Cl₂ hazard and all paint-remover formulations are appropriately labeled. This is a critical duty because one sixth of the 180 million kg of CH₂Cl₂ produced in the United States is being consumed in the rapidly expanding paint-remover market.¹³

This investigation was supported in part by contract HSM-99–72–84 from the National Institute of Occupational Safety and Health.

Anthony Wu, PhD, and Sally A.Graff provided technical assistance.

References

1. Stewart RD, Fisher TN, Hosko MJ, et al: Carboxyhemoglobin elevation after exposure to dichloromethane. Science 176:295–296, 1972.

2. Stewart RD, Fisher TN, Hosko MJ, et al: Experimental human exposure to methylene chloride. Arch Environ Health 25:324–348, 1972.

3. Kubic VL, Anders MW, Engel RR, et al: Metabolism of dihalomethanes to carbon monoxide. Drug Metabolism and Disposition. 2:53–57, 1974.

4. Ratney RS, Wegman DH, Elkins HB: In vivo conversion of methylene chloride to carbon monoxide. Arch Environ Health 28:223–226, 1974.

5. Fodor GG, Prajsnar D, Schlipkoter H: Endogenous CO formation by incorporated halogenated hydrocarbons of the methane series. Staub Reinhaltung der Luft 33:260–261, 1973.

6. DiVincenzo GD, Hamilton ML: Fate and disposition of methylene chloride in the rat. Toxicol Appl Pharmacol 32:385–393, 1975.

7. Stewart RD, Hake CL, Forster HV, et al: Methylene chloride: development of a biologic standard for the industrial worker by breath analysis, report No. NIOSH-MCOW-ENVM-MC-74–9. Cincinnati, National Institute of Occupational Safety and Health, 1974.

8. Stewart RD, Baretta ED, Platte LR, et al: Carboxyhemoglobin levels in american blood donors. JAMA 229:1187–1195, 1974.

9. Aronow WS, Harris CN, Isbell MW, et al: Effect of freeway travel on angina pectoris. Ann Intern Med 77:669–676, 1972.

10. Aronow WS, Isbell MW: Carbon monoxide effect on exercise-induced angina pectoris . Ann Intern Med 79:392–395, 1973.

11. Anderson EW, Andelman RJ, Strauch JM, et al: Effect of low-level carbon monoxide exposure on onset and duration of angina pectoris: A study in ten patients with ischemic heart disease. Ann Intern Med 79:46–50, 1973.

12. Scharf SM, Thames MD, Sargent RK: Transmural myocardial infarction after exposure to carbon monoxide in coronary artery disease: Report of a case. N Engl J Med 291:85–86, 1974.

13. Paint-remover sales take off. Chemical Week 65–66, Oct 20, 1971.

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