We first counted the number of indoor carbon monoxide poisoning incidents and related cases, and then estimated the overall and year-by-year morbidity and mortality in Jinan City from 2007 to 2021. Furthermore, we describe the spatiotemporal characteristics of CO poisoning. Spatially, we compared urban-rural differences by drawing maps. In terms of time, we describe the prone time of CO poisoning in year, month and hour distributions respectively. Finally, we explored the individual risk-to-CO exposure-disease-death relationship and performed trend fitting. Method steps and detailed description are as follows:
research participants
This study was approved by the Ethics Committee of Shandong University School of Public Health (identification code LL20220922), and informed consent was obtained from all participants and/or their legal guardians. The study complied with the Declaration of Helsinki.
Background information on Jinan
Jinan is located at 36.40° north latitude and 110.00° east longitude, with a total area of 8177.21 kilometers2. It is divided into ten administrative districts including five urban area districts of Lixia, Shizhong, Huaiyin, Tianqiao, Licheng and five rural area districts of Changqing, Zhangqiu, Jiyang, Pingyin and Shanghai15. It is a temperate monsoon climate with uneven distribution of seasons and nearly 150 days in winter (November to March of the following year)16. The lowest temperature in winter is often below -10°C, and there are occasional cold waves, snowstorms and other extreme weather in January and December.according to Regulations on the Management of Urban Centralized Heating in Jinan City17urban areas provide central heating services from March 15 to November 15 (121 days per year), while in rural and urban-rural fringe areas, coal heating is often used due to substandard facilities, which greatly increases the risk of CO poisoning risk.
data collection
The daily meteorological data from 2007 to 2021 are provided by the China Meteorological Data Sharing Service System Network18including daily mean temperature, daily maximum temperature and daily minimum temperature.
Summary of daily non-occupational carbon monoxide poisoning incidents in Jinan from 2007 to 2021 from China Public Health Emergency Information System19,20. The system operates on the basis of 91 notifying hospitals and consolidated outbreak/incident profiles for infectious diseases, foodborne diseases, waterborne diseases, occupational poisoning, environmental emergencies (indoor and outdoor air pollution), and other unknown public health events. Indoor environmental emergencies involve non-occupational CO poisoning. The survival time of carbon monoxide poisoning cases collected by us includes the date of onset (time of visit), location and location of poisoning, cause of poisoning, population exposed to carbon monoxide, and severity of poisoning.
The main causes of non-occupational carbon monoxide poisoning in Jinan City include household coal-fired heating, restaurant gas leakage, suicide, etc. (caused by other events). From 2007 to 2021, households using coal for heating accounted for 81% of carbon monoxide poisoning, which is the main cause of carbon monoxide poisoning. Therefore, this study analyzes the spatio-temporal characteristics and occurrence trends of household coal-fired heating.
Analysis of epidemiological characteristics
A descriptive epidemiological method was used to analyze the time, space and population characteristics of carbon monoxide poisoning caused by household coal heating. Exposure rate, incidence density (cases) and death rate were measured using the following formulas:
$$\mathrmExposure\,rate= \frac\mathrm\,CO \,exposed\,number of individuals\mathrmyear\,population\,\times\,\mathrmtime\ ,(\mathrmyears)\,\times\, \mathrm100,000$$
(Unit: per 100,000 person-years).
$$\mathrmIncidence\,density= \frac\mathrm\,CO\,poisoning\,number of cases\mathrmper year\,population\,\times\,\mathrmtime\ ,(\mathrmyears)\,\times \,\mathrm100,000$$
(Unit: per 100,000 person-years).
$$\mathrmDeath rate\, rate= \frac\mathrm\,CO \,poisoning\,deaths\mathrmyear\,population\,\times\, \mathrmtime \, (\mathrmyears)\,\times \,\mathrm100,000$$
(Unit: per 100,000 person-years).
Statistical Analysis
We built an Excel database and analyzed the data using descriptive epidemiological methods. Spatial analysis was performed by RStudio version 3.5.1. Statistical analysis was performed by SPSS 21.0 (SPSS Inc., Chicago, IL, USA). Chi-square tests were used to compare rates, and the statistical significance level was set at 0.05.
Ethics approval and consent to participate
This study was approved by the Ethics Committee of Shandong University School of Public Health (identification code LL20220922), and informed consent was obtained from all participants and/or their legal guardians. The study complied with the Declaration of Helsinki.
