Risk Factors for Non-Occupational Carbon Monoxide Poisoning: Anshan Prefecture, Liaoning Province, China, 2011–2012

BACKGROUND Carbon monoxide (CO) poisoning can be fatal but is preventable. From October 2010 to February 2011, Anshan Prefecture reported 57 cases of non-occupational CO poisoning in District A, with two deaths. We conducted an investigation to identify risk factors and recommend preventive measures. METHODS We defined a possible case of non-occupational CO poisoning as onset of at least two of the following symptoms: fatigue, headache, dizziness, nausea, vomiting, cyanosis, loss of consciousness, coma, and shock from October 1, 2010, to February 28, 2011, in a resident of Anshan Prefecture with non-occupational exposure to CO poisoning. We defined a probable case as onset of at least one of the following symptoms: cyanosis, loss of consciousness, coma and shock, plus at least one of the following symptoms: fatigue, headache, dizziness, nausea, vomiting, among possible cases. A confirmed CO poisoning case was a possible case or probable case plus hemoglobin (Hb) CO higher than 10%. We searched for cases by reviewing medical records and records of hyperbaric oxygen tank usage. In a case-control investigation, we compared home heating practices of 30 case-persons and 120 control-persons who were individually matched to each case by neighborhood. RESULTS Overall, 56% (39/70) of case-patients' households burned coal for home-heating. In the case-control investigation, 40% (12/30) of case-persons' households compared with 5.8% (7/120) of control-persons' households placed stoves in bedrooms (Mantel-Haenszel odds ratio [ORM-H] = 11, 95% confidence interval [CI] = 3.0-41); 53% (16/30) of case-patients' households and 33% (40/120) of control-patients' households did not extinguish the fire before sleeping (ORM-H = 3.6, 95% CI = 1.1-12); 13% (4/30) of case-patients' households and 3% (4/120) of control-patients' households had not installed the ventilation pipe vertically (ORM-H = 7.3, 95% CI = 1.0-56). Overall, 77% (23/30) of case-patients' households and 39% (47/120) of control-patients' households had at least one of those three risk factors (ORM-H = 10, 95% CI = 2.5-40; population attributable risk percentage: 78%). CONCLUSIONS Dangerous practices with coal-burning stoves inside the home accounted for the majority of CO poisoning incidents. Community health centers should provide instruction to and supervision of residents on proper installation and use of home heating stoves as well as inspection of installation.