Deaths from Carbon monoxide poisoning in Iran between 2011 and 2018- An ecological study

Abstract

Background: Carbon monoxide (CO) poisoning, as one of the lethal poisoning, is responsible for a large percentage of poisonings and accidental deaths. Since the investigation of the mortality and the distribution of CO poisoning deaths in Iranian provinces is still unknown and no study has investigated so far, this study was conducted to determine the trend of mortality rate changes due to CO poisoning by Spatio-temporal analysis in Iran from 2011 to 2018.

Methods: An ecological study was conducted based on data from the reports of at the National Center for Statistics of Iran for eight years from 21 March 2011 to 21 March 2018. The number of deaths due to CO poisoning and the annual mortality rates of CO poisoning per 100,000 population were calculated. The Spatio-temporal analysis used to determine the spatial and temporal distribution of deaths.

Results: A total of 6078 deaths were reported due to CO poisoning that 4497 death were male (74%) and 1596 were female (26%) from 2011 to 2018. In both sexes, the mortality rate due to CO poisoning was 1.26 from 2011 to 0.91 in 2018. According to the results, the overall male-to-female ratio was 2.8. The mortality rate due to CO Poisoning had a decreasing trend. However, this trend did not have a linear trend (p=0.37). Our results showed that most of the deaths due to CO poisoning are higher in the northern and western provinces of Iran.

Conclusion: This study is one of the first studies to compare the spatial and temporal mortality rates due to CO poisoning in Iran. Paying attention to general education about the principles of safety in the installation of heaters and the use of the gas networks, continuous and accurate monitoring of the installation and operation of CO-producing, and the use of sensitive alarms can reduce mortality and morbidity due to CO poisoning.

Background

Poisoning is one of the major concerns of the health system in every country. In Iran, poisoning is one of the leading causes of hospitalization and death(1), and about 20% of hospital admissions are due to poisoning (2). Carbon monoxide (CO) poisoning, as one of the lethal poisoning, is responsible for a large percentage of poisonings and accidental deaths (3). It is colorless and odorless and is the result of incomplete combustion produced by motor vehicles, coal stoves, stoves, and heaters(4, 5).

CO poisoning accounts for about 50,000 deaths annually in the US emergency department, with 38 % of deaths due to CO poisoning between the ages of 10 and 19 years(6, 7). In Asia, CO poisoning is one of the leading causes of suicide(8). Some studies in Iran have also shown that about 10% of poisonings in Iran are due to CO and reported mortality rate 3.1 per 100,000 population in 2016 (9). Another study showed that the mortality ratio of this poisoning was 11.6 per 1000 deaths in 2016(10).

Iran, as one of the main producers of natural gas, has extensive use of natural gas domestically. Despite the widespread use of gas-fired devices and their possible risks, especially the sudden death of CO poisoning in Iran, the mortality and the distribution of CO poisoning deaths in this country is still unknown and no study has investigated so far. To show the trends of CO poisoning deaths with the increased use of urban gas based on Iranian provinces over time, the purpose of this study was to determine the trend of mortality rate changes due to CO poisoning by Spatio-temporal analysis in Iran from 2011 to 2018.

Methods

Study area:

Iran is a country in the Middle East with a total area of 1 648 195 km². According to the last National Census in 2016, the total population of Iran is approximately 80 million. Iran has a common border with Armenia, Turkmenistan, and Azerbaijan in the North; Afghanistan and Pakistan in the East; the Persian Gulf and Gulf of Oman in the South; and Iraq and Turkey in the West.

Study design and used dataset:

An ecology analysis was conducted based on the data obtained from the Iran official reports on population. Deaths from CO poisoning data were obtained based on the reports of at the Iranian legal medicine organization (ILMO) for eight years from 21 March 2011 to 21 March 2018. At the end of each year, the ILMO publishes deaths from CO reports on its website, by gender and province(11). Access to this data is free for all. Confirmation of CO deaths is based on autopsy evidence, examining the bodies of victims by a specialist, and an emergency medical report after being transferred death cases to provincial ILMO. This method of confirmation in all provinces is based on similar guidelines, and there is no difference in how to diagnose the cause of death. These cases were classified based on the International Classification of Diseases, Tenth Revision (ICD-10) code X47(12), and verified by ILMO. The number of deaths due to CO poisoning and the annual mortality rates of CO poisoning per 100,000 population were calculated. Calculation of rates per 100,000 inhabitants in Iran was performed using census data from 2011 to 2018.

 Temporal trend analysis

 To assess the trend of reported mortality rates the line plot of reported cases during the understudied period was used.

Spatial analysis

 The unit of spatial analysis was different provinces of Iran. A Choropleth map was used to describe the distribution of mortality rate of CO poisoning cases (per 100,000 people) each year by the population of the province. This index calculated for each province as this formula:

Hotspot identification

To identify clusters of fatal cases due to CO poisoning in different years, the Hotspot analysis was used. Hot spots present the clusters of under study event. This analysis performed using the Getis-Ord Gi statistics. A high score on this index combined with a lower p-value indicates the clustering of understudy event. The Gi statistics formula is as follows:

 Where Xj is the mortality rate of under study event for province j, w i.j is the spatial weight between provinces i and j, and n is the total number of provinces. X and S, are calculated as follows:

In terms of hot spot analysis, the α: 0.01 and 0.05 were considered as significant level. All analyses were performed using ArcGIS 10.5 and Excel 2010.

Results

Descriptive analysis:

As showed in table 1, A total of 6078 deaths were reported due to CO poisoning that 4497 death were male (74%) and 1596 were female (26%) from 2011 to 2018. In both sexes, the mortality rate of CO poisoning was 1.26 from 2011 to 0.91 in 2018. According to the results, the overall male-to-female ratio was 2.8. As figure 1 demonstrated, the average mortality rate due to CO poisoning in Semnan, North Khorasan, and Qazvin, Zanjan, Alborz, and Tehran was higher than in other provinces of Iran.

Table 1. Number of death and mortality rates due to CO poisoning by gender in Iran between 2011 and 2018

Temporal analysis:

As figure2, in both sexes, the time trend in mortality rate due to CO Poisoning had a fluctuation over time. The lowest and highest mortality rate was reported in 2014 and 2011, respectively, in both sexes. In addition to this visual inspection analysis, the mortality rate due to CO Poisoning had a decreasing trend during the understudied period.  

Spatial distribution:

Figure 3 shows that some provinces have had higher mortality rates than others in different years. Among all provinces of Iran, North Khorasan, Semnan, Qom, Qazvin, Zanjan, Chaharmahal Bakhtiari, and Tehran had the highest mortality rates between 2011 and 2018. The lowest mortality rates also found in southern provinces of Iran, such as Kerman, Sistan and Baluchestan, Hormozgan, Bushehr, and Khuzestan.

Hot Spots:

In 2011, Qazvin and Qom were considered as Hot spot. It means that the mortality rate due to CO poisoning (per 100,000) in these provinces was significantly higher than the overall average of the country, so these provinces were considered as hot-spots (p<0.05). In 2012, the Qom was considered as hot-spot area (p<0.05). Mazandaran, Qazvin, Tehran, Qom, and Lorestan provinces were considered as Hot spot in 2013(p<0.05). Among provinces, Alborz had the Most mortality rate in comparison to the country average, so were considered as hot-spots (p<0.01) in 2014. although there were not any Hot spot areas in 2015, there were Hot-spots in Qazvin, Tehran, Qom, and Lorestan provinces in 2013(p<0.01). Also, among provinces, Mazandaran, Tehran, and Qom were considered as Hot spot in 2017 (p<0.05), and finally, in 2018, Alborz and Qom were considered as hot-spots (p<0.05). (Figure 4)

Discussion

CO poisoning is considered as one of the health emergencies for its lethal nature as well as its subsequent complications if survived. This study aimed to investigate the trend of deaths due to CO poisoning among provinces of Iran. The results showed that the mortality rate due to CO poisoning was from 1.26 from 2011 to 0.91 per 100,000 population in 2018, and the mortality trend did not change in these eight years. Although there are not studies in the same period to compare these findings with others, some studies indicate that the trend of changes has not been significant before 2011. In a study carried out in Iran in 2010(13), the mortality rate due to CO poisoning was between 1.1 and 2.2 per 100,000, which was not statistically significant between 2002 and 2006. In another study by Nazari et al.(14), the mortality rate due to CO poisoning was less than 1 per 1,000 people, with no statistical difference between 2003 and 2008. Since the ILMO approves the data in this study and there is no underreporting in the data collection, it seems that overall, there has not been little change in the mortality rate of CO poisoning in Iran over the years.

Our results demonstrated both the number of deaths and the mortality rate due to CO poisoning were higher in men than women each year. Consistent with our study, in studies of Mirahmadizadeh et al. in 2016(15), Nazari et al. (14), and Shokrzadeh et al. in 2017(16) have shown mortality rate due to CO poisoning was higher in men than women. Previous studies in other countries have also indicated these differences (17-20). Although these differences are unclear, it seems men have more risky activities, such as working indoors or in garages with combustible tools than women that increase the exposure duration(21, 22). Studies to compare occupational among men and women who died, the mechanism of the effect of CO on Dying, and its differences between women and men, may help to understand this difference better.

This study showed that most of the deaths due to CO poisoning are higher in the northern and western provinces of Iran. As the northern and western provinces of Iran have a colder climate and many fatality cases accrued in the cold season (9, 23, 24), the use of gas heaters in these areas is higher than elsewhere, which could increase the exposure of the population to CO. To confirm this, a study conducted in the northern and western parts of Iran has shown that most deaths due to CO poisoning and have been in cold seasons (14, 25). On the other hand, increasing the number of villages and cities with the urban gas distribution network in the north and west of Iran can also increase the number of poisoning cases and deaths due to CO. lack of understanding in using the gas and how to properly maintain appliances may contribute to risk(14). In support of this, our study showed that the mortality rate due to CO poisoning is lower in southern provinces of the country with warmer climates and provinces with less gas distribution network than in other regions of Iran.

There were some limitations to our study. First, this study is based on data annually published by ILMO by province and gender. The classification of this data is not based on other variables. We did not have additional data on seasonal distribution, occupational distribution, demographic characteristics, and the number of poisoned cases, which could better explain the epidemiological characteristics. Second, there were no adequate studies using data other than ILMO to compare these findings with the theme.

Conclusion

This study is one of the first studies to compare the spatial and temporal mortality rates due to CO poisoning in Iran. As our findings showed, mortality changes over time were not significant, and the mortality rate was higher in the northern and western provinces than in the south of Iran. Paying attention to general education about the principles of safety in the installation of heaters and the use of the gas networks, continuous and accurate monitoring of the installation and operation of CO-producing, and the use of sensitive alarms can reduce mortality and morbidity due to CO.

Abbreviations

CO: carbon monoxide

ILMO: Iranian legal medicine organization

Declarations

Ethics approval and consent to participate:

All data in this study are freely available by the Forensic Medicine Organization and the National Center for Statistics of Iran, and there are no specific ethical aspects to publishing the results. All data was accessed as part of ongoing public health surveillance activities, and all data were obtained as part of ongoing public health surveillance activities and therefore considered exempt from consent to participate.

Consent for publication:

Not applicable.

Availability of data and materials: The datasets used and analyzed during the current study are available from the corresponding author on reasonable request.

Competing interests: The authors declare that they have no competing interests.

Funding: none

Authors' contributions: Danial Rahimi interpreted the data. Yousef Alimohamadi contributed to the statistical analysis, and Ahmad Mehri participated in the planning, writing, and was the lead editor of the project and contributed to the writing. All authors read and approved the final manuscript.

Acknowledgment

This study conducted by using data from Iranian legal medicine organization and National Center for Statistics of Iran from 2011 to 2018.

References

1. Moradi M, Ghaemi K, Mehrpour O. A hospital base epidemiology and pattern of acute adult poisoning across Iran: a systematic review. Electronic physician. 2016;8(9):2860.
2. Bagheri P, Sepand M. A meta analytical study of intentional and accidental non-food poisoning incidences in Iran (1991-2013). Koomesh. 2015;16(3):443-53.
3. Raub JA, Mathieu-Nolf M, Hampson NB, Thom SR. Carbon monoxide poisoning—a public health perspective. Toxicology. 2000;145(1):1-14.
4. LaSala G, McKeever R, Okaneku J, Jacobs D, Vearrier D. The epidemiology and characteristics of carbon monoxide poisoning among recreational boaters. Clinical toxicology. 2015;53(2):127-30.
5. Kao LW, Nañagas KA. Carbon monoxide poisoning. Emergency Medicine Clinics. 2004;22(4):985-1018.
6. Hampson NB, Weaver L. Carbon monoxide poisoning: a new incidence for an old disease. Journal of the Undersea and Hyperbaric Medical Society. 2007.
7. Mendoza JA, Hampson NB. Epidemiology of severe carbon monoxide poisoning in children. Undersea and hyperbaric medicine. 2006.
8. Wu KC-C, Chen Y-Y, Yip PS. Suicide methods in Asia: implications in suicide prevention. International journal of environmental research public health. 2012;9(4):1135-58.

9. Khadem-Rezaiyan M, Afshari R. Carbon monoxide poisoning in Northeast of Iran. Journal of Forensic and Legal Medicine. 2016;41:1-4.
10. Hosseininejad SM, Aminiahidashti H, Goli Khatir I, Ghasempouri SK, Jabbari A, Khandashpour M. Carbon monoxide poisoning in Iran during 1999–2016: A systematic review and meta-analysis. Journal of Forensic and Legal Medicine. 2018;53:87-96.
11. Iranian legal medicine organization 2020 [Available from: https://en.lmo.ir/.
12. International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10)-WHO Version 2016 [Available from: https://icd.who.int/browse10/2016/en.
13. Rahimi M, Aghabiklooei A, Nasouhi S, Mashayekhian M, Ghoochani A, Yousefi Y, et al. A 5-year assessment on carbon monoxide poisoning in a referral center in Tehran-Iran. International Journal of Preventive Medicine. 2019;10(1).
14. Nazari J, Dianat I, Stedmon A. Unintentional carbon monoxide poisoning in Northwest Iran: A 5-year study. Journal of Forensic and Legal Medicine. 2010;17(7):388-91.
15. Mirahmadizadeh A, Faramarzi H, Hadizadeh E, Moghadami M, Fardid M, Seifi A. A Yearlong Epidemiologic Study on Unintentional Acute Carbon Monoxide Poisoning in Fars Province, Southwest Iran. Asia Pacific Journal of Medical Toxicology. 2016;5(1):15-9.
16. Shokrzadeh M, Zarei H, Seyyedghasemi NS, Badeli A, Jalilian J, Falahtalab FE, et al. Epidemiology of death caused by carbon monoxide poisoning in Golestan province, Iran, 2010-2015. Journal of Mazandaran University of Medical Sciences. 2017;27(150):181-6.
17. Mott JA, Wolfe MI, Alverson CJ, Macdonald SC, Bailey CR, Ball LB, et al. National Vehicle Emissions Policies and Practices and Declining US Carbon Monoxide–Related Mortality. JAMA. 2002;288(8):988-95.
18. Hays P, Bornstein RA. Failed suicide attempt by emission gas poisoning. The American journal of psychiatry. 1984.
19. Cook M, Simon PA, Hoffman RE. Unintentional carbon monoxide poisoning in Colorado, 1986 through 1991. American journal of public health. 1995;85(7):988-90.
20. Cobb N, Etzel RA. Unintentional carbon monoxide—Related deaths in the United States, 1979 through 1988. JAMA. 1991;266(5):659-63.
21. Centers for Disease C, Prevention USA. Carbon monoxide--related deaths--United States, 1999-2004. MMWR: Morbidity and mortality weekly report. 2007;56(50):1309-12.
22. Yoon SS, Macdonald SC, Parrish RG. Deaths from unintentional carbon monoxide poisoning and potential for prevention with carbon monoxide detectors. JAMA. 1998;279(9):685-7.
23. Dianat I, Nazari J. Characteristics of unintentional carbon monoxide poisoning in Northwest Iran - Tabriz. International Journal of Injury Control and Safety Promotion. 2011;18(4):313-20.
24. Farzaneh E, Seraji FN, Valizadeh B. Epidemiology of carbon monoxide gas poisoning deaths in Ardabil city, 2008-13. International Journal of Research in Medical Sciences. 2015;3(4):929-32.
25. Yari M, Fouladi N, Ahmadi H, Najafi F. Profile of acute carbon monoxide poisoning in the west province of Iran. Journal of the College of Physicians and Surgeons Pakistan. 2012;22(6):381-4.