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Catalytic converter and suicide risk
Letters to the Editor
Catalytic converter and suicide risk Accident and after removal from his car, which was found in a garage with the engine running and a hosepipe connecting the exhaust pipe to the interior of the vehicle. A suicide note had been left. It was subsequently confirmed that he had been in the car for about 1 hour. On arrival in the emergency department high-flow oxygen was instituted by paramedical staff. On examination he was tachycardic but normotensive, responded to questions appropriately, and had neither abnormal neurological signs nor papilloedema. Cardiac monitoring and a 12-lead electrocardiograph revealed no ischaemia. Blood was taken for initial carboxyhaemoglobin (COHb), urea, electrolytes, and glucose. Intravenous mannitol 1 g/kg was given prophylactically. The case was discussed with the local hyperbaric oxygen unit and it was thought appropriate to consider transfer early the next morning. High-flow oxygen by mask was continued overnight and the patient recovered uneventfully. The initial COHb level was 6-6% (Instrumentation Laboratories IL 482 Co-oximeter, Warrington, UK). This was surprisingly low given the exposure time; a lethal concentration can be reached within 10 minutes. A level of 4-6% would be normal for an urban smoker and 1-3% in a non-smoker. Enquiry revealed that our patient’s car was equipped with a 3-way catalytic converter, which at maximum efficiency would be expected to remove approximately 90% of the carbon monoxide and other toxic compounds from the exhaust effluent (data from Sun Electric, SIR-A 26-year-old man presented to Emergency department about 10 minutes
soon see a
reduction in this method of CO poisoning due to current
changes in environmental legislation.
our
Kings Lynn, Norfolk, UK):
Carbon monoxide (CO) has an affinity for haemoglobin some 240 times that of oxygen and causes a distortion and shift to the left in the oxygen dissociation curve. This renders tissues anoxic and is the mechanism behind the long-term sequelae of poisoning. CO has an elimination half-life of 250 minutes when breathing room air, shortened to 59 minutes when breathing 100% high-flow oxygen, and shortened further by instituting hyperbaric oxygen. A pressure of 2-5atmospheres reduces the elimination half life to 22 minutesAdding 5-7% carbon dioxide to the breathed air would reduce the elimination half-life to 12 minutes but this exacerbates the acidosis of severe poisoning. Since January, 1993, to comply with exhaust-gas emission requirements, all new cars sold in the UK are fitted with catalytic converters.3 These cylindrical devices contain a meshwork of ceramic material onto which is sprayed a mixture of rhodium and platinum that catalyses the incomplete combustion of the engine to minimise the toxic byproducts and maximise carbon dioxide and water production. CO poisoning accounts for some 3800 deaths per year in the US;4 half of all poisoning deaths. In the UK, 1000 deaths per year are thought to result from CO intoxication. We are unaware of any similar case reported in this country to date although there has been a single study in the US.S We hope we will
A S
Wagg, S J B Aylwin
Medical Unit, Royal London
Hospital Trust, Whitechapel, London E1 1BB, UK
Meredith TJ, Vale A. Carbon monoxide poisoning. BMJ 1988; 296: 77-79. Ilano AL, Raffin TA. Management of carbon monoxide poisoning. Chest 1990; 97 (1): 165-69. European Community Directive 91/441 L242, Aug 30, 1991. Statutory Instrument 1992, 2909. Grimm PS, Gottlieb LJ, Boddie A, et al. Hyperbaric oxygen therapy. JAMA 1989; 263: 2216-20. Lester D. Changing rates of suicide by car exhaust in men and women in the United States after car exhaust was detoxified. Crisis 1989; 10
1 2
3 4 5
(2): 164-68.
Electromagnetic fields and childhood cancer SiR-There have now been ten studies on residential exposure magnetic fields and cancer in children. These studies have been reviewed extensively, and all have their weaknesses-in potential systematic error, in small numbers, or both.l Three Nordic studies have been published or are in press.2-4 All three took advantage of the Nordic population registry system, thereby minimising the risk of selection bias. All three studies also used a novel approach to exposure assessment. They were based on residential magnetic field exposure generated by high-voltage transmission lines, which made it feasible to estimate in-home magnetic fields at different times. Thus, the design of these studies made it possible to overcome some difficulties faced by previous investigators. The three studies were planned in concert with a view to perhaps pooling the results. However, owing to several local circumstances, the studies differ in certain design aspects. The Finnish study is a cohort study, whereas the two others are case-control studies. The Danish and Finnish studies use the entire populations, whereas the Swedish study is restricted to people living close to power lines. There are also certain differences in the primary data and methods used for magnetic field calculations. Despite the differences, it seems reasonable to assume that chance is the main reason for differences in the relative risk estimates across the three studies. With this assumption, a pooled analysis may be used to address the problem of small numbers in each of the individual studies. Thus, we analysed the combined evidence of the three Nordic studies on the hypothesis that magnetic fields have a role in the development of cancer. to
RR = relative risk estimate.
Table: Results of three Nordic studies
1295
Catalytic converter and suicide risk Accident and after removal from his car, which was found in a garage with the engine running and a hosepipe connecting the exhaust pipe to the interior of the vehicle. A suicide note had been left. It was subsequently confirmed that he had been in the car for about 1 hour. On arrival in the emergency department high-flow oxygen was instituted by paramedical staff. On examination he was tachycardic but normotensive, responded to questions appropriately, and had neither abnormal neurological signs nor papilloedema. Cardiac monitoring and a 12-lead electrocardiograph revealed no ischaemia. Blood was taken for initial carboxyhaemoglobin (COHb), urea, electrolytes, and glucose. Intravenous mannitol 1 g/kg was given prophylactically. The case was discussed with the local hyperbaric oxygen unit and it was thought appropriate to consider transfer early the next morning. High-flow oxygen by mask was continued overnight and the patient recovered uneventfully. The initial COHb level was 6-6% (Instrumentation Laboratories IL 482 Co-oximeter, Warrington, UK). This was surprisingly low given the exposure time; a lethal concentration can be reached within 10 minutes. A level of 4-6% would be normal for an urban smoker and 1-3% in a non-smoker. Enquiry revealed that our patient’s car was equipped with a 3-way catalytic converter, which at maximum efficiency would be expected to remove approximately 90% of the carbon monoxide and other toxic compounds from the exhaust effluent (data from Sun Electric, SIR-A 26-year-old man presented to Emergency department about 10 minutes
soon see a
reduction in this method of CO poisoning due to current
changes in environmental legislation.
our
Kings Lynn, Norfolk, UK):
Carbon monoxide (CO) has an affinity for haemoglobin some 240 times that of oxygen and causes a distortion and shift to the left in the oxygen dissociation curve. This renders tissues anoxic and is the mechanism behind the long-term sequelae of poisoning. CO has an elimination half-life of 250 minutes when breathing room air, shortened to 59 minutes when breathing 100% high-flow oxygen, and shortened further by instituting hyperbaric oxygen. A pressure of 2-5atmospheres reduces the elimination half life to 22 minutesAdding 5-7% carbon dioxide to the breathed air would reduce the elimination half-life to 12 minutes but this exacerbates the acidosis of severe poisoning. Since January, 1993, to comply with exhaust-gas emission requirements, all new cars sold in the UK are fitted with catalytic converters.3 These cylindrical devices contain a meshwork of ceramic material onto which is sprayed a mixture of rhodium and platinum that catalyses the incomplete combustion of the engine to minimise the toxic byproducts and maximise carbon dioxide and water production. CO poisoning accounts for some 3800 deaths per year in the US;4 half of all poisoning deaths. In the UK, 1000 deaths per year are thought to result from CO intoxication. We are unaware of any similar case reported in this country to date although there has been a single study in the US.S We hope we will
A S
Wagg, S J B Aylwin
Medical Unit, Royal London
Hospital Trust, Whitechapel, London E1 1BB, UK
Meredith TJ, Vale A. Carbon monoxide poisoning. BMJ 1988; 296: 77-79. Ilano AL, Raffin TA. Management of carbon monoxide poisoning. Chest 1990; 97 (1): 165-69. European Community Directive 91/441 L242, Aug 30, 1991. Statutory Instrument 1992, 2909. Grimm PS, Gottlieb LJ, Boddie A, et al. Hyperbaric oxygen therapy. JAMA 1989; 263: 2216-20. Lester D. Changing rates of suicide by car exhaust in men and women in the United States after car exhaust was detoxified. Crisis 1989; 10
1 2
3 4 5
(2): 164-68.
Electromagnetic fields and childhood cancer SiR-There have now been ten studies on residential exposure magnetic fields and cancer in children. These studies have been reviewed extensively, and all have their weaknesses-in potential systematic error, in small numbers, or both.l Three Nordic studies have been published or are in press.2-4 All three took advantage of the Nordic population registry system, thereby minimising the risk of selection bias. All three studies also used a novel approach to exposure assessment. They were based on residential magnetic field exposure generated by high-voltage transmission lines, which made it feasible to estimate in-home magnetic fields at different times. Thus, the design of these studies made it possible to overcome some difficulties faced by previous investigators. The three studies were planned in concert with a view to perhaps pooling the results. However, owing to several local circumstances, the studies differ in certain design aspects. The Finnish study is a cohort study, whereas the two others are case-control studies. The Danish and Finnish studies use the entire populations, whereas the Swedish study is restricted to people living close to power lines. There are also certain differences in the primary data and methods used for magnetic field calculations. Despite the differences, it seems reasonable to assume that chance is the main reason for differences in the relative risk estimates across the three studies. With this assumption, a pooled analysis may be used to address the problem of small numbers in each of the individual studies. Thus, we analysed the combined evidence of the three Nordic studies on the hypothesis that magnetic fields have a role in the development of cancer. to
RR = relative risk estimate.
Table: Results of three Nordic studies
1295