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Thomas F. Schrager,Ph.D, Editor

About Cambridge Toxicology Group, Inc.


An Unusual Case of Carbon Monoxide Poisoning

Pierre L. Auger,1 Benoît Levesque,1 Richard Martel,2 Henri Prud'homme,1 David Bellemare,3 Claude Barbeau,4 Pierre Lachance,5 and Marc Rhainds1

1Direction de santé publique de la région de Québec, Service de Santé Environnmentale, Beauport, Québec, Canada
2INRS-Géoressources, Sainte-Foy, Québec, Canada
3CLSC Haute-Ville, Santé au travail, Charlesbourg, Québec, Canada
4Département de chimie, Faculté des Sciences et de Génie, Université Laval, Sainte-Foy, Québec, Canada
5Centre Hospitalier Universitaire de Québec, Québec, Canada


Carbon monoxide, a gas originating from incomplete combustion of carbon-based fuels, is an important cause of human deaths. In this paper, we describe an unusual carbon monoxide poisoning in a dwelling without obvious sources of combustion gases, for which two adults had to be treated in a hyperbaric chamber. Carbon monoxide readings were taken in the house and in the neighboring homes. Methane gas and nitrogen oxide levels were also monitored in the house air. Soil samples were collected around the house and tested for hydrocarbon residues. The investigation revealed the presence of a pocket of carbon monoxide under the foundation of the house. The first readings revealed carbon monoxide levels of 500 ppm in the basement. The contamination lasted for a week. The investigation indicated that the probable source of contamination was the use of explosives at a nearby rain sewer construction site. The use of explosives in a residential area can constitute a major source of carbon monoxide for the neighboring populations. This must be investigated, and public health authorities, primary-care physicians, governmental authorities, and users and manufacturers of explosives must be made aware of this problem. Key words: carbon monoxide, dwelling, explosives, geology, poisoning. Environ Health Perspect 107:603-605 (1999) . [Online 16 June 1999]



CO poisoning is difficult to diagnose. Symptoms are nonspecific, and in many cases, it likely remains undetected, particularly if there is no obvious exposure to combustion gases. Even if all the underlying mechanisms are not understood, such as the significance of the geological characteristics and the conditions in which the explosives were used, the results of the investigation and the review of existing literature indicate that the use of explosives in a residential area can be a major source of CO exposure for the population. In the present case, as in the investigation by Dougherty et al. (10), the poisoning was serious enough to lead to hospitalization. Therefore, it is more than likely, given the significant use of explosives in our industrialized world, that many other unidentified incidents have occurred. More must be done to further investigate and better understand this problem. In the meantime, public health authorities, primary-care physicians, governmental authorities, and explosives manufacturers and users must be made aware that the use of explosives in residential areas may lead to significant CO exposure for the neighboring populations.



Upon completion of this manuscript, we were made aware of a similar incident that occured at 6:00 p.m. on 10 November 1998 in a small town in the province of Québec, Canada. In this case, six houses were involved. CO readings varied from 125 to 600 ppm (Model 3005; Ames Multigas, Annacis Island, British Columbia, Canada). Six occupants of 16 were intoxicated (COHb ranging from 2 to 24%), and three of them had to be transferred to the hyperbaric chamber. No obvious causes could explain the CO buildup in these houses, other than nearby rock blasting that took place during the day to connect the local sewage system to the main municipal system. Again, excavations were conducted to create the natural funnel needed to ventilate the sewer system. The next morning, CO readings were negative in all six houses, and rock blasting operations then resumed. CO control measurements were concurrently conducted. Readings were normal in five houses, while they were high in the sixth house. One reading in a nearby manhole was as high as 1,100 ppm. The next morning (12 November), CO readings were still at 52 ppm in that house. Ventilating shafts had to be installed and pushed under the slab, and mechanical ventilation had to be applied to eliminate all residual CO. This case reinforces the urgency for public health authorities and other bodies concerned to address this problem (13).


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