Acute Carbon Monoxide Poisoning in Shandong, China: An Observational Study
Carbon monoxide (CO) poisoning remains a significant public health concern globally, contributing to a substantial number of accidental injuries and fatalities. In China, particularly in rural and suburban areas, CO poisoning is a persistent issue due to the reliance on coal and charcoal for heating, especially during the winter months. This study provides a comprehensive analysis of the epidemiological features and clinical characteristics of acute CO poisoning in Shandong province, China, during the winter of 2019-2020. The findings highlight the prevalence, severity, regional differences, and environmental factors associated with CO poisoning, offering valuable insights for public health interventions and clinical management.
Background and Significance
CO poisoning is a leading cause of accidental injuries worldwide, often resulting in severe or long-term neurological damage. In China, non-occupational sources of CO poisoning, such as poorly maintained heating systems and cooking appliances, are the primary contributors to CO exposure. Despite rapid urbanization and economic development, rural areas in northern China continue to rely on coal and charcoal for heating, which, when inadequately combusted, can lead to unintended CO accumulation. Unlike other countries where suicide is a major cause of CO poisoning, accidental exposure due to heating equipment malfunction and poor ventilation is the predominant cause in China.
Shandong province, located in eastern China, has a temperate monsoon climate and a large rural population. The province’s economic development has not been evenly distributed, with urban areas benefiting from centralized heating services while rural areas still depend on coal-based heating. This disparity makes Shandong an ideal region for studying the epidemiology of CO poisoning. This study aims to fill the gap in provincial-level data on acute CO poisoning by conducting a retrospective analysis of cases reported between November 2019 and April 2020.
Methods
The study collected clinical data from patients diagnosed with acute CO poisoning across 16 municipal cities in Shandong province. Data were obtained from hyperbaric oxygen (HBO) therapy departments in hospitals, with weekly reports submitted by the directors of each city’s HBO Medicine Branch. Cases were classified into three severity levels—mild, moderate, and severe—based on clinical manifestations and arterial carboxyhemoglobin (COHb) levels. Mild cases presented with symptoms such as headache, weakness, nausea, and vomiting, with COHb levels exceeding 10%. Moderate cases exhibited severe headache, irritability, impaired judgment, and reduced awareness, with COHb levels above 30%. Severe cases involved coma, myocardial injury, respiratory failure, and COHb levels exceeding 50%.
Statistical analysis was performed using GraphPad Prism software. Differences in the proportion of CO poisoning cases were evaluated using two-way ANOVA with Bonferroni post hoc tests. Spearman correlation analysis was used to examine the relationship between environmental temperature and the number of confirmed CO poisoning cases. A significance level of 0.05 was set for all statistical tests.
Results
General Characteristics
A total of 21,088 cases of acute CO poisoning were diagnosed during the study period. Based on Shandong’s population of 101.5 million in 2020, the incidence of acute CO poisoning was approximately 0.021%. The majority of cases (63%, n = 13,378) were mild, while 27% (n = 5,635) were moderate, and 10% (n = 2,075) were severe. Two significant peaks in the number of cases were observed: the first during the third week of November 2019 and the second during the third week of January 2020. These peaks coincided with the onset of winter heating and the Chinese Lunar New Year, respectively.
Regional Differences
Coastal cities, particularly Qingdao and Yantai, reported a higher number of CO poisoning cases compared to inland areas. The four coastal cities of Qingdao, Yantai, Rizhao, and Weihai accounted for 42% of all cases (n = 8,827). In contrast, inland cities such as Jining, Dezhou, and Liaocheng reported fewer cases, with only three cities exceeding 1,000 cases. The distribution of case severity varied across regions, with coastal cities reporting a higher proportion of mild and moderate cases. Statistical analysis revealed significant differences in the number of cases among the 16 municipal cities, as well as differences in the severity of cases.
Correlation with Environmental Temperature
The number of CO poisoning cases was significantly higher during the colder months of November to January (n = 16,198, 77%) compared to February to April (n = 4,890, 23%). A strong negative correlation was observed between the mean daily temperature and the number of confirmed cases (Spearman r = -0.9429, P = 0.0167), indicating that lower temperatures were associated with an increased incidence of CO poisoning.
Discussion
The study underscores the significant public health burden of CO poisoning in Shandong province, particularly during the winter months. The reliance on coal and charcoal for heating in rural areas, combined with inadequate ventilation and equipment maintenance, contributes to the high incidence of CO poisoning. The findings align with previous studies that highlight the role of environmental temperature in influencing the prevalence of CO poisoning.
The most severe complication of CO poisoning is delayed neurological sequelae (DNS), which can lead to long-term disability or death. Early intervention with hyperbaric oxygen (HBO) therapy has been shown to reduce the risk of DNS, emphasizing the importance of timely medical care. However, the study’s data collection was limited to patients who received HBO therapy, potentially underestimating the true incidence of CO poisoning, particularly in rural areas where access to medical facilities is limited.
The regional disparities in CO poisoning cases reflect differences in economic development, healthcare access, and heating practices. Coastal cities, with better healthcare infrastructure and higher economic status, reported more cases, likely due to better data collection and reporting. In contrast, inland and rural areas may have underreported cases due to limited access to medical services.
Public health interventions aimed at reducing CO poisoning should focus on improving heating equipment maintenance, increasing awareness of CO risks, and promoting the use of CO detectors in homes. Community health centers can play a crucial role in educating residents about safe heating practices and the importance of proper ventilation.
Limitations
The study has several limitations. First, the data were collected from hospitals providing HBO therapy, which may not capture all CO poisoning cases, particularly those treated in primary care settings or resulting in pre-hospital deaths. Second, the study lacked long-term follow-up, limiting the ability to assess the incidence of DNS and mortality. Third, the data primarily represent suburban and rural areas, potentially excluding cases from urban centers with centralized heating systems.
Conclusions
This study provides valuable insights into the epidemiology of acute CO poisoning in Shandong province, China. Mild cases accounted for the majority of confirmed cases, with coastal cities reporting a higher incidence than inland areas. The findings highlight the importance of environmental factors, particularly temperature, in influencing the prevalence of CO poisoning. Public health interventions should focus on improving heating practices, increasing awareness of CO risks, and ensuring timely access to medical care. Future research should aim to establish a national CO poisoning registry to better understand the epidemiology and develop effective prevention strategies.
doi.org/10.1097/CM9.0000000000001942
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