Introduction:
Carbon Monoxide (CO) which is called a "silent killer" is a colorless, odorless, also a non-irritable gas. [1] CO is mainly formed by incomplete combustion of organic compounds, fire smoke, vehicle exhaust, and improper use of heating devices. [2] Claude Bernard in 1865 was first described as CO poisoning. [3]
CO poisoning is responsible for almost 50,000 deaths yearly in the US, with 38% of death as a result of CO poisoning between the age group of 10-19 years. [4, 5] In Iran, it was reported that the estimated rate of CO poisoning was 38.91 per 100,000 population with a mortality rate of 11.6 per 1000 deaths in 2016. [6] Another study in 2016 reported a mortality rate of 3.1 per 100,000 for CO poisoning. [7] According to the report of the Legal Medicine Organization in 2004, CO poisoning was the third cause of unintentional harm in Iran after motor-vehicle accidents and burning. [8]
CO binds to blood hemoglobin (Hb) with high affinity and forms Carboxyhemoglobin (COHb). [9] In healthy and non-smoking individuals, the COHb concentration is less than 2%, and in smoking individuals, it is less than 15%. At COHb levels above 10 %, neurological symptoms including headache, dizziness, and nausea are detected. At COHb levels of 30% to 50%, confusion, motor paralysis, and heart and respiratory rates increase are observed. The COHb levels over 50% are life-threatening and considered CO-poisoning. [10-12] Tissue hypoxia is the chief effect of CO poisoning, which is because of COHb formation. It reduces the oxygen transport capacity and leads to inadequate tissue oxygenation. [10, 11]
There is no new information about the prevalence of carbon monoxide poisoning in Mazandaran province during this period. What is certain is that ignorance and unawareness is the main cause of CO poisonings and deaths due to CO gas. Therefore, this study aimed to epidemiologically investigate CO poisoning in Mazandaran province during yeas 2016 to 2018.
Materials and Methods
The present study is a descriptive-analytical and retrospective study on the information obtained from the files of the deceased individuals who died due to carbon monoxide poisoning in the forensic medicine of Mazandaran province during the years 2016 to 2018. The exclusion criteria were patients whose files were incomplete and the required information cannot be obtained. The research tool was a checklist designed by the researchers. The first part of the checklist includes demographic information such as age, sex, and level of education, and the second part consists of information including place of death, CO-producing agent, physical examination findings, the findings of the autopsy, and laboratory findings.
Statistical analysis
All checklist information was analyzed using SPSS software version 16. Frequency percentages were used for descriptive data. The Chi-square test was used to compare variables. Values were significant at p less than 0.05.
Ethical consideration
The study is approved by the ethics committee of Mazandaran University of Medical Sciences. The study was performed according to the Helsinki principles of ethics.
Results
In this study, 83 deaths due to CO poisoning were recorded and descriptive values ??related to the demographic and clinical characteristics of these three years of study can be seen in Table 1. Most of these people were over 50 years old (32.5%), 81.9% of them were men, and 61.4% of them were married. The level of education in 92.8% of them was reported to be less than a bachelor's degree and most of these poisonings occurred in the bedroom (66.3%). 56.6% of these poisonings were due to town gas poisoning and 56.6% of deaths were reported as groups death. The bruises color was rosette in 53% of the deaths. The Carboxyhemoglobin levels in most of them were +2 (63.9%) and most deaths occurred in January (19.3%).
| Table 1: Demographic and Clinical Characteristics of Carbon Monoxide Deaths |
| Variabe |
No. (%) |
Age group |
|
0-10 |
2 (2.4) |
11-20 |
7 (8.4) |
21-30 |
18 (21.7) |
31-40 |
15 (18.1) |
41-50 |
13 (15.7) |
> 50 |
27 (32.5) |
unknown |
1 (1.2) |
Gender |
|
Male |
68 (81.9) |
Female |
15 (18.1) |
Education level |
|
Less than Bachelor |
77 (92.8) |
Bachelor and Master |
0 (0) |
Doctorate and higher |
0 (0) |
Unknown |
6 (7.2) |
Place of poisoning |
|
Bathroom |
4 (4.8) |
Bedroom |
55 (66.3) |
Out of home |
17 (20.5) |
Unknown |
7 (8.4) |
Cause of poisoning |
|
Town gas |
47 (56.6) |
Capsule gas |
10 (12) |
Charcoal and wood |
15 (18.1) |
Unknown |
11 (13.3) |
Bruising color |
|
Rosette |
44 (53) |
Cherry red |
14 (16.9) |
Pink |
7 (8.4) |
Grey |
2 (23.8) |
Unknown |
16 (19.3) |
Blood Carboxyhemoglobin level |
|
+1 |
10 (12) |
+2 |
53 (63.9) |
+3 |
14 (16.9) |
Unknown |
6 (7.2) |
Death type |
|
Individual |
26 (31.3) |
Group |
47 (56.6) |
Unknown |
10 (12) |
The month of poisoning |
|
April |
13 (15.7) |
May |
0 (0) |
June |
3 (3.6) |
July |
0 (0) |
August |
3 (3.6) |
September |
1 (1.2) |
October |
2 (2.4) |
November |
10 (12) |
December |
7 (8.4) |
January |
16 (19.3) |
February |
12 (14.5) |
March |
13 (15.7) |
Unknown |
3 (3.6) |
Marital status |
|
Single |
26 (31.3) |
Married |
51 (61.4) |
Unknown |
6 (7.2) |
According to the results of this study, the total number of deaths due to CO poisoning was 83, according to the results can be said that although the number of deaths was higher in 2018 compared to other years and lower in 2017 than in other years, this difference was not statistically significant (Table 2).
| Table 2: The total number of deaths by year of occurrence and the difference between the years |
| Variable |
Years, No. (%) |
Value |
Sig. |
2016 |
2017 |
2018 |
Total |
Number of deaths |
25 (30.1) |
21 (25.3) |
37 (44.6) |
83 (100) |
5.01 |
0.082 |
Table 3 shows the results for the age group of deaths related to CO poisoning. According to the test results, it can be seen that most age groups in the three years had a statistically significant difference from each other (p-value = 0.014) so in 2016, 2017, and 2018 the most deaths related to CO were reported for the age groups of 41-50 (32%), 21-30 (28.6%) and over 50 years (48.6%) (Table 3).
| Table 3: The age group of deaths, gender, and marital status by year of occurrence and the difference between the years |
| Groups |
Years, No. (%) |
Value |
Sig. |
2016 |
2017 |
2018 |
Age |
0-10 |
1 (4) |
1 (4.8) |
0 (0) |
19.79 |
0.014 |
11-20 |
1 (4) |
5 (23.8) |
1 (2.7) |
21-30 |
5 (20) |
6 (28.6) |
7 (18.9) |
31-40 |
4 (16) |
4 (19) |
7 (18.9) |
41-50 |
8 (32) |
1 (4.8) |
4 (10.8) |
> 50 |
4 (24) |
3 (14.3) |
18 (48.6) |
Unknown |
0 (0) |
1 (4.8) |
0 (0) |
Gender |
Male |
21 (84) |
16 (76.2) |
31 (83.8) |
0.71 |
0.76 |
Female |
4 (16) |
5 (23.8) |
6 (16.2) |
Marital status |
Single |
8 (32) |
10 (47.6) |
8 (21.6) |
5.1 |
0.076 |
Married |
12 (48) |
10 (47.6) |
29 (78.4) |
Unknown |
5 (20) |
1 (4.8) |
0 (0) |
The gender of deaths due to CO poisoning by year is shown in Table 3. According to the obtained results, it can be seen that most of the deaths in all three years were related to the male gender. It can be said that during all three years, the frequency of male in deaths was higher than females, however, there was no significant during these years.
The results showed that in these three years, most of the deaths occurred in married individuals (p-value = 0.076) (Table 3).
The results of this study showed that, except for unknown cases, in all three years the most prevalent level of education was less than a bachelor's degree (Table 4).
| Table 4: The level of education in deaths related to carbon monoxide poisoning over the years |
| Level of Education |
Years, No. (%) |
2016 |
2017 |
2018 |
Less than a Bachelor's degree |
23 (92) |
18 (85.7) |
36 (97.3) |
Bachelor and Master degree |
0 (0) |
0 (0) |
0 (0) |
Doctorate or higher |
0 (0) |
0 (0) |
0 (0) |
Unknown |
2 (8) |
3 (14.3) |
1 (2.7) |
According to the results obtained from the place of poisoning, it can be seen that most of the deaths were related to the bedroom. It can also be said that the locations of poisoning during these three years were not significantly different from each other (p-value = 0.26) (Table 5).
| Table 5: The place, reason, and type of poisoning in different years |
|
Years, No. (%) |
Value |
Sig. |
2016 |
2017 |
2018 |
Place of poisoning |
|
|
|
|
|
Bathroom |
3 (12) |
0 (0) |
1 (2.7) |
4.86 |
0.26 |
Bedroom |
14 (56) |
12 (57.1) |
29 (78.4) |
Out of home |
7 (28) |
4 (19) |
6 (16.2) |
Unknown |
1 (4) |
5 (23.8) |
1 (2.7) |
Reason of poisoning |
City gas |
11 (44) |
14 (66.7) |
22 (59.5) |
13.9 |
0.004 |
Capsule gas |
7 (28) |
1 (4.8) |
2 (5.4) |
Charcoal and wood |
4 (16) |
0 (0) |
11 (29.7) |
Unknown |
3 (12) |
6 (23.6) |
2 (5.4) |
Type of Death |
Individual |
8 (32) |
7 (33.3) |
11 (29.7) |
0.73 |
0.69 |
Group |
14 (56) |
9 (42.9) |
24 (64.9) |
Unknown |
3 (12) |
5 (23.8) |
2 (5.4) |
According to the results obtained from Table 5, it can be seen that the causes of poisoning during these three years were statistically significant (p-value = 0.004). According to these results, city gas has been the most common cause during these three years. But for the second reason of poisoning in 2016, capsule gas was the cause of 28% of the deaths, while in 2018, charcoal and wood (29.7%) were in the second place.
The results showed that most of the deaths during these three years happened in groups and the number of deaths was not statistically significant (p-value = 0.73) (Table 5).
The bruises color of poisoning cases was the same during these three years and did not differ significantly (P = 0.09). Most of the bruises have been rosette during these three years, and the cherry red color has been the second most prevalent color of bruises during these three years (Table 6).
| Table 6: The color of bruises in deaths related to carbon monoxide poisoning over the years |
| Color of Bruises |
Years, No. (%) |
Value |
Sig. |
2016 |
2017 |
2018 |
Rosette |
18 (72) |
9 (42.9) |
17 (45.9) |
9.44 |
0.09 |
Cherry red |
2 (8) |
3 (14.3) |
9 (24.3) |
Pink |
0 (0) |
1 (4.8) |
6 (16.2) |
Grey |
0 (0) |
0 (0) |
2 (5.4) |
Unknown |
5 (20) |
8 (38.1) |
3 (8.1) |
According to the results, the level of carboxyhemoglobin in the blood of those who died due to poisoning during these three years has been significantly different (p-value = 0.002). During these three years, the level of carboxyhemoglobin + 2 has the highest number of cases. While in 2016 and 2017 the carboxyhemoglobin level of +3 and in 2018, the carboxyhemoglobin level of +1 was in the second rank (Table 7).
| Table 6: The Carboxyhemoglobin level in deaths related to carbon monoxide poisoning over the years |
| Carboxyhemoglobin level |
Years, No. (%) |
Value |
Sig. |
2016 |
2017 |
2018 |
+1 |
1 (4) |
0 (0) |
9 (24.3) |
15.02 |
0.002 |
+2 |
19 (76) |
10 (47.6) |
24 (64.9) |
+3 |
5 (20) |
7 (33.3) |
2 (5.4) |
Unknown |
0 (0) |
4 (19) |
2 (5.4) |
The results showed that the number of deaths due to CO poisoning during the three years were significantly different from each other (p-value = 0.001) and it can be said that in 2016, the most deaths related to the month April and February, in 2017 related to March and in 2018 related to November and January (Table 8).
| Table 8: The month of carbon monoxide poisoning by years |
| Month |
Years, No. (%) |
Value |
Sig. |
2016 |
2017 |
2018 |
April |
6 (24) |
4 (19) |
3 (8.1) |
15.02 |
0.002 |
May |
0 (0) |
0 (0) |
0 (0) |
June |
0 (0) |
1 (4.8) |
2 (5.4) |
July |
0 (0) |
0 (0) |
0 (0) |
August |
0 (0) |
0 (0) |
3 (8.1) |
September |
0 (0) |
0 (0) |
1 (2.7) |
October |
0 (0) |
2 (9.5) |
0 (0) |
November |
1 (4) |
0 (0) |
9 (24.3) |
December |
3 (12) |
2 (9.5) |
2 (5.4) |
January |
2 (8) |
2 (9.5) |
12 (32.4) |
February |
7 (28) |
3 (14.3) |
2 (5.4) |
March |
4 (16) |
6 (28.6) |
3 (8.1) |
Unknown |
2 (8) |
1 (4.8) |
0 (0) |
Discussion
Carbon monoxide poisoning is a major health problem and maybe the cause of many deaths due to poisoning. In fact, carbon monoxide may be responsible for more than half of the reported fatal poisonings [13]. Many studies in Iran have shown that carbon monoxide poisoning is one of the three main causes of poisoning [6, 14], and determining the prevalence of this poisoning is one of the requirements for developing appropriate prevention programs at the national level. The present study investigated the prevalence of this poisoning during the years 2016 to 2018 in Mazandaran province and determined the factors affecting it.
The results of the demographic information of this study showed that in this study, 83 deaths were recorded due to CO poisoning. Most of these people were over the age of 50 and most of them were male and married. Also, the level of education was mostly less than a bachelor's degree. Most of which occurred in the bedroom. The main poisoning agent was city gas and the deaths mainly occurred in groups. The main bruise color was rosette and the hemoglobin level of most of them was +2. Most of these deaths occurred in January.
The results of this study showed that a significant difference was observed in the age of occurrence of poisoning in this study. The highest frequency of poisoning was related to the ages over 50 years and in the second rank was the age group of 21-30 years. According to Khadem-Rezaian et al study the mortality rate was higher in the > 60 age group. [7] Another study by Dianat et al. in Tabriz city reported that the death rate was greatest for those in the age group over 64 years. [15] In Long et al. on data collected from the Global Burden of Diseases for the years 1990 and 2017, it was reported that the 15-49 age group and after that 50-59 age group were related to the highest rate of death. [16] In contrast to the present study, in Hosseininejad et al.'s systematic review of Iran, most of the death cases were about 30 years old. [6] In another study by Yari et al. in the western province of Iran the main mortality was observed in the age groups of 20-30 years and less than 10 years. [17] The reason should be considered as the demographic, social, cultural, and economic differences in Iran.
There was a significant difference between the number of males and females among dead people. The results showed that poisoning was higher in males than females, which was in line with the results of the Khadem Rezaian et al. study which showed that the fatality rate was higher in males (5.4%) than in females (4.4%). [7] In a study by Long et al. on data collected from the Global Burden of Diseases for the years 1990 and 2017, the rate of death as a result of CO poisoning was higher in males (26.32% and 23.73%, respectively) than in females (11.89 and 11.75, respectively), similar to the present study [16]. In an epidemiological 10 years study in Jordan, it was also shown that most of the victims of CO poisoning were male. [18] In Janík et al.'s study was also more male death (59%) occurred due to CO poisoning. [19] One of the reasons for the high frequency of men can be a higher incidence of job problems among men. In addition, the results of this study showed a significant difference in the rate of deaths in married people, which is in line with the results of the Khadem Rezaian et al. study. [7] Shokrzadeh et al. study also showed the victims were mostly married. [20] However, in Hosseininejad et al.'s study, 52.74% of the victims were single. [6]
The level of education of dead people was less than a bachelor's degree, which was in line with the results of the Khadem Rezaian et al. study. [7] Hosseininejad et al. study also demonstrated that in most of the victims, the level of education was secondary school [6]. The level of education as an influential factor can be effective in the rate of poisoning. It can be said that with increasing the level of education of a community the level of awareness and information of that community also increases which can reduce mortality due to CO poisoning.
The location of poisoning of these deaths was not significantly different during these years and most of them were reported in the bedroom and the least in the bathroom. According to Shokrzadeh et al.'s study among females, most of the death place was home or bathroom and among male victim, it was mostly home. [20] In Dianat et al.'s study, the bathroom and the living room were the most places of death among victims. [15] The majority of cases in the bedroom are caused by heaters, which indicates a lack of awareness of the proper use of this device. [17, 20]
In the present study, the cause of poisoning was significantly different during these years which was mostly related to city gas. Reasons such as the development of the gas supply network, the use of gas appliances with technical defects, and non-compliance with safety and standard conditions in their use can be considered as the main reasons. One of the preventive solutions in this regard can be a warning and educational programs in this regard through mass media, press, and social networks. In Dianat et al.'s study, domestic gas appliances and then gas water heaters were the main reason for poisoning. [15] Janík et al. study reported that the majority of CO-related deaths were related to coal gas, motor vehicle exhaust fumes, fire smoke, charcoal, and gas and wood-burning appliances respectively. [19] Coal or charcoal and fire are the main reason for CO poisoning in Li et al.'s study in China. [21] In Shokrzadeh et al.'s study, the main reason for CO poisoning was defined as heaters. [20]
Most of the poisonings that occurred in this study occurred in the cold months of the year. The user of heating devices will increase in these seasons, and also closed windows and poor ventilation can be other contributing factors. On the other hand, due to the greater use of fossil fuels in the cold season, CO poisoning in winter is. Nazari et al. study also reported that the rate of CO poisoning was higher in winter. [14] Shokrzadeh et al. study demonstrated that 75% of the cases were happened in cold months. [20] Another study by Yari et al. showed that autumn and winter were the most seasons related to Co poisoning. [17] Li et al. defined that the maximum death occurring month was January, followed by February and December. [21]
The result also showed the most carboxyhemoglobin level in these three years was + 2. In Janík et al.'s study, the mean carboxyhemoglobin level of blood was 66%. [19] In Shotar et al.'s study, the mean carboxyhemoglobin level was 68% ± 13% and ranged from 12%-83%. [18]
Conclusion
According to the results of this study, carbon monoxide poisoning is one of the factors that kills a number of people in this province every year, especially in cold seasons. As a result, paying attention to this issue can play an important role in preventing CO poisoning. Therefore, attention should be paid to issues such as educating and informing the public through public media and educational environments about the dangers and ways of carbon monoxide poisoning in homes and vehicles, as well as creating proper ventilation for bedrooms, bathrooms, and other places and not using water heaters in the bathroom, checking the chimneys of houses in cold seasons and visiting them periodically. In addition, raising the level of education and awareness of the people can reduce the number of poisoning cases in the province.
This information can be implemented by health policymakers in implementing appropriate community-based interventions. We believe that almost all cases of accidental carbon monoxide poisoning can be prevented by general education on prevention programs and regulations related to carbon monoxide devices.
Limitations
This study faced limitations such as lack of access to all members of the statistical community due to lack of referral to forensic medicine, lack of examination in neighboring provinces, and lack of access to details of deceased information. In future studies, it is recommended that the study be conducted in a community with more samples and more detailed information to investigate other factors affecting carbon monoxide poisoning in this province and neighboring provinces or the whole country.
Conflicts of interest:
There are no conflicts of interest in the present study.
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