Explosives used for blasting operations in civil engineering works can generate large volumes of carbon monoxide (CO). The production of 1024 L of CO per kilogram of explosives blasted is theoretically possible. CO can migrate a considerable distance in the fractured rock of the blasted areas and then infiltrate closed spaces (sewage systems, manholes, basements of houses). In the Province of Quebec, in the last 10 years, seven people were poisoned by CO in their houses to the extent that they had to be treated in a hyperbaric chamber. Underground conduits broken by blasting, filling around underground conduits in road or house trenches, or fractured rock created by blasts between houses or between a house and a road are the different CO pathways identified in the Quebec incidents. Field tests done by our group show that (i) the structural geology of the rock formation (schistosity, family of joints and fractures) controls the direction and extent of gas migration in fractures generated by blasts; (ii) the confinement of the rock can affect the quantity of gas migrating in the fractured rock; (iii) significant concentrations of CO may persist in the fractured rock 7 days after a blast; (iv) advection is the initial mechanism of CO migration immediately after a blast, and the distance of migration varied from 8 m in the fractured rock to 20 m in the fills of a road trench; and (v) further CO migration by diffusion up to 15 m in the induced fractures and 30 m in fills may occur in the 3 days following a blast.Key words: carbon monoxide, blasting, poisoning, enclosed spaces, gas migration, house.
Karting is a recreational activity of increasing popularity and it is often practiced indoors leading to build up of toxic gases in ambient air. This study was realised to verify the level of exposure to carbon monoxide (CO) in ten male racers (Age: 15 to 49 years old) during a 45-min race. The alveolar concentration of CO (alvCO) for each participant was measured before and after the race. The ambient CO level was determined continuously from the start to the end of the race with two detectors. Mean ambient air CO concentration was 41 ppm and the average increase of alvCO for the ten subjects was 16.2 ppm corresponding to about 3% COHb. Based on these results and on the Coburn model, a reference limit of 25 ppm was suggested for a 1 h exposure during indoor karting. At the request of the public health authorities, some modifications were made to the karts, to the CO monitoring surveillance system and to the ventilation system of the building. CO concentrations were monitored thereafter. The guideline of 25 ppm for 60 min was always respected.
A questionnaire was sent to all members of the Association des médecins d’urgence du Québec during March 1997 to estimate their abilities to diagnose, treat and follow-up carbon monoxide (CO) poisoning. The questionnaire comprised case histories about frequent or important types of poisoning of which four were related to CO. Questions were asked about diagnosis, investigation, treatment or follow-up. Of the 450 members of the Association, 109 responded to the questionnaire (24.2%). In the physicians’ answers to three case histories that were presented to measure their ability to identify CO poisoning, this diagnosis was correctly identified by 80.7, 97.2 and 71.6% of physicians, respectively, for each case history. Concerning the investigation, 97.2% of physicians chose one good answer and 25.7% chose two among two possible, carboxyhaemoglobin level being the most frequent one (87.2%). Concerning treatment, 99.1% of physicians chose one good answer and 57.8% chose two among two possible, immediate prescription of 100% oxygen by mask being the most frequent one (98.2%) and transfer of the patient to the hyperbaric chamber the second one (58.7%). Concerning the follow-up of the patient, 61.5% of physicians chose the good answer, which was to see the patient in 2 weeks. In conclusion, more than 70% of the physicians were able to identify this diagnosis and deficiencies in the management were mainly noted in the treatment and follow-up phases. These results may represent an overestimate of the reality.
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