Epidemiological characteristics of pesticide poisoning in Jiangsu Province, China, from 2007 to 2016

To investigate the characteristics of pesticide poisoning in Jiangsu province and provide a scientific basis for measures for the prevention of pesticide poisoning. Information from pesticide poisoning report cards from 2007 to 2016 was derived from the Occupational Disease and Occupational Health Information Monitoring System, and the characteristics of pesticide poisoning patients were assessed via descriptive analysis. A total of 30,789 pesticide poisoning cases were reported in Jiangsu Province. Of these cases, 23,557 were non-occupational poisonings, accounting for 76.5% of the reported cases. There were 1705 deaths from pesticide poisoning, and the fatality rate was 5.5%. Numerous cases occurred in northeast Jiangsu. Pesticide poisoning cases were primarily concentrated in individuals 36–60 years of age. Pesticide poisoning primarily occurred in the summer. The top types of pesticides causing poisoning were organophosphates. The fatality rate of intentional pesticide poisoning was the lowest among the age group of 0 to 14 years, while the highest was noted among people over 61 years. Therefore, pesticide poisoning is a major problem in Jiangsu Province. We need to strengthen the management of highly toxic pesticides and implement effective health education on the use of pesticides.

www.nature.com/scientificreports www.nature.com/scientificreports/ To further understand the current situation, pathogenesis, characteristics and distribution of pesticide poisoning in Jiangsu, we obtained detailed data on pesticide poisoning in Jiangsu Province from 2007 to 2016 through the ODSRS for a thorough and descriptive analysis. These findings could be used to encourage the development and implement a strategy for the safe handling, use and disposal of pesticides and reduce the incidence of pesticide poisonings.

Results
Basic information on pesticide poisoning. From 2007 to 2016, there were 30,789 cases of pesticide poisoning in Jiangsu Province. Among these cases, 12,867 involved males, and 17,922 involved females. In total, 1705 cases ended in death, yielding a mortality rate of 5.5%, including 765 males and 940 females. The number of deaths attributed to non-occupational pesticide poisoning was 1,666, which led to a fatality rate of 7.1%. The total mortality rate of male pesticide poisoning was significantly higher than that of female pesticide poisoning (χ 2 = 6.28, P < 0.05) (Table 1).
Regional distribution of pesticide poisoning. Compared with occupational pesticide poisoning, the number of cases, number of deaths and mortality rate of non-occupational pesticide poisoning are relatively high, which indicates that the main problem of pesticide poisoning in Jiangsu Province is non-occupational pesticide poisoning. The most ubiquitous cases of pesticide poisoning occurred in Xuzhou, Nantong, and Yancheng. The number of cases of pesticide poisoning in Nanjing was the lowest (73 cases), comprising 0.2% of all cases in Jiangsu Province. In addition, 8 cases of pesticide poisoning were unknown. The top three pesticide poisoning deaths occurred in Nantong, Xuzhou and Huai'an (Table 2 and Fig. 1).
Distribution of the types of pesticides causing poisoning. The   www.nature.com/scientificreports www.nature.com/scientificreports/ were organophosphates, herbicides and fungicides, and other insecticides. The number of poisonings by organophosphate pesticides was the highest (18,548), accounting for 60.2% of all cases, followed by 3,595 herbicides and fungicides (11.7%) and 2,703 other insecticides (8.8%). Among the organophosphate pesticides, methamidophos and dichlorvos resulted in the most pesticide poisoning cases. Herbicide and fungicide pesticide poisoning was primarily focused on paraquat and other herbicides ( Table 3). The pesticide with the highest rate of poisoning was paraquat, which also had the highest fatality rate (11.6%). Among the seven categories, organophosphate pesticides triggered the highest (6.5%) fatality rate (χ 2 = 942.10, P < 0.001).  Others unspecified 1125 78 6.9 Table 3. Pesticide types involved in pesticide poisoning in Jiangsu Province. *wo-sided χ 2 test.
www.nature.com/scientificreports www.nature.com/scientificreports/ seasonal distribution of pesticide poisoning. Pesticide poisoning occurred throughout the year during the study period in Jiangsu Province. The highest number of reported cases occurred in summer, with 12.3% and 19.8% of all cases occurring in July and August, respectively. The lowest number of cases occurred in January (3.3%), as shown in Fig. 2A. Occupational pesticide poisoning occurred most often in the summer, with 8190 cases representing 34.8% of the total occupational pesticide poisoning cases (Fig. 2B). Meanwhile, the cases of non-occupational pesticide poisoning were primarily concentrated in summer, with 5505 cases constituting 76.1% of all non-occupational pesticide poisoning cases (Fig. 2C). Total pesticide poisoning cases were highest in July and lowest in January (Fig. 2D). A similar distribution was observed for deaths due to non-occupational pesticide poisoning (Fig. 2E). Deaths induced by occupational pesticide poisoning were highest in August and lowest in March (Fig. 2F).
Age distribution of pesticide poisoning cases. Pesticide poisoning cases were predominantly concentrated in the age group of 15-60 years. The number of cases in the age group of 36-60 years was the highest, accounting for 47.9% of all cases (Table 4). Occupational pesticide poisoning cases were primarily found in the age group of 36-60 years, and the number of cases in this population accounted for 65.4% of all occupational poisoning cases. Deaths induced by pesticide poisoning were concentrated in people over 36 years old, most of whom were older than 61 years, accounting for 46.9% of all deaths. Fewer deaths caused by pesticide poisoning were noted in the group less than 35 years of age, only representing 14.1% of total deaths. Comparably, a distribution pattern was found in non-occupational pesticide poisoning and reported deaths from occupational pesticide poisoning. Among the number of intentional pesticide poisoning deaths in different age groups, the lowest number occurred in people 0-14 years old, and the highest occurred in people over 61 years old. The number of intentional pesticide poisoning cases increased gradually with age. There were significant differences in the distribution of mortality among different age groups (χ 2 = 540.84, P < 0.001).
Stratified analysis of pesticide poisoning in different economic conditions. Based on the above studies, we found significant differences in pesticide poisoning populations based on age (P < 0.001) and sex (P < 0.05). Age and sex may be mixed factors, affecting the overall effect of the region in the preliminary analysis. Therefore we use age and sex as factors and stratified Chi-square tests to analyse the impact of regional factors on the risk of disease at different ages and genders. We divided the study population in southern and northern   www.nature.com/scientificreports www.nature.com/scientificreports/ Jiangsu into different subgroups according to age and sex (Table 5). For people aged 36-60 and over 61 years, a significant difference in pesticide poisoning was noted between northern and southern Jiangsu (OR = 0.69, 95% CI = 0.57-0.83, P < 0.001; OR = 0.78, 95% CI = 0.65-0.92, P < 0.001). Similarly, female pesticide poisoning in northern and southern Jiangsu exhibited statistical significance (OR = 0.72, 95% CI = 0.61-0.84, P < 0.001).

Discussion
The results of the reported pesticide poisoning cases from 2007 to 2016 showed that the incidence of pesticide poisoning in Jiangsu Province was decreasing. One study found that the health effects of a more comprehensive ban on highly toxic pesticides is needed to create a balance between increased agricultural costs and reduced health care costs and deaths 12 . The number of reported cases and mortality of non-occupational pesticide poisoning are higher than those of occupational pesticide poisoning, which indicates that the primary problem of pesticide poisoning in Jiangsu is non-occupational in origin. This finding is consistent with the conclusions found in similar Zhejiang Province. The two provinces both mainly plant rice and have consistent poisoning from the same pesticides. The rate of consumption of insecticides is the largest, followed by herbicides and rodenticides, while organophosphorus insecticides, pyrethroids and other insecticides are the main pesticides. Non-occupational poisoning is mainly triggered by suicide or accidental ingestion 5,13 . Given that non-occupational pesticide poisoning is easily detected, the case fatality rate is correspondingly high. However, occupational pesticide poisoning mostly occurs at occupational sites and workers are more likely to receive timely treatment after poisoning. Thus, the mortality of occupational pesticide poisoning is accordingly maintained at a low level. There are also reported sex differences in pesticide poisoning 14 . Women's vulnerability to pesticides may have psychological, behavioural and socio-economic roots. In addition, women have a lower proportion of self-protective behaviours than man when applying pesticide 15 . In the light of the facts outlined above, sex-related working conditions may increase pesticide exposure among females 16 .
This study revealed that the use of pesticides in Jiangsu Province was ubiquitous, and there were reports of pesticide poisoning cases in various cities. Reportedly, the case fatality of pesticide poisoning in the developing world is higher than Western countries, which is attributed to the following reasons: the high toxicity of locally available poisons, the difficulty of transporting patients to the hospital over long distances, the lack of health care workers compared with the large number of patients, and the lack of facilities and antidotes 17 . The occurrence of pesticide poisoning has certain regional differences. The number of pesticide poisoning cases in northern Jiangsu exceeds that in southern Jiangsu, which may be relevant to the economic base and the poor level of industrial and agricultural development in the region 2,11 . Accordingly, it is important to optimize the control of pesticide hazards in northern Jiangsu.
The study found that from 2007 to 2016, the cases of organophosphate pesticide poisoning in Jiangsu were the highest, among which dichlorvos, methamidophos and omethoate were principal culprits. Among the seven classes of pesticides, the class that contributed to the greatest mortality rate was organophosphate pesticide and the specific agent that led to the highest mortality was paraquat, which is consistent with the conclusions of Roberts MD 4 . This finding illustrates that the safe use and management of organophosphate pesticides should be strengthened at the peak of their usage, and the application of highly toxic pesticides, such as paraquat, should be given more attention 4,12 . In terms of the age of those affected by occupational or non-occupational pesticide poisoning, individuals 36-60 years old were primarily affected although the mortality rate was highest in people over 60 years old. Studies have shown that socially disadvantaged groups are at a higher risk of pesticide poisoning 18 . With economic development, increasing number of adolescents are gradually leaving rural areas and entering the city to work 19 . Thus, the aged have consequently become the main farming work force, and there are more opportunities for pesticide contact. Meanwhile, as individuals grow older, their physical function and resistance decrease. Additional factors include depression and other illnesses which can lead to suicide by oral pesticides in the elderly 20 . Hence, to reduce the occurrence of occupational pesticide poisoning, it is critical to conduct health education for middle-aged and elderly people, publicize the correct use of pesticides and spraying methods, and focus on the utilization of personal protective devices when spraying high-toxic pesticides 21 .
The seasonal distribution of pesticide poisoning indicates that there are significant temporal changes in occupational pesticide poisoning in Jiangsu, which mainly occurred from July to September, accounting for 76.1% of all occupational pesticide poisoning cases. This finding is also consistent with the conclusions of Zhejiang 11 . This  www.nature.com/scientificreports www.nature.com/scientificreports/ seasonal increased use of pesticides may be relevant to a higher pest burden during summer and autumn leading to an increased need and subsequent use in the amount pesticide application. The higher temperature in summer and autumn increases the volatilization of pesticides and enhances the chance of pesticide exposure. Meanwhile, farmers lack training in protection knowledge, lack self-protection awareness, and do not wear individual protective equipment as required. Therefore, in summer and autumn, it is imperative to promote the standardization of the production, transportation and use of pesticides and stress the importance to personal protection. There are more female cases of occupational pesticide poisoning than male cases, which is different from previous reports 18,21 . It is possible that more male migrant workers are located in rural areas of Jiangsu.
Studies have presented that the absolute number of suicide deaths of China ranks first in the world, and pesticide poisoning ranks first among methods of suicide 6 . According to the data, the number of cases of intentional pesticide poisoning accounted for 64.8% of the total number of pesticide poisoning cases, and the number of intentional pesticide poisoning deaths constituted 93.1% of all deaths. This study also found that the case fatality rate of intentional pesticide poisoning increased by age, especially in the elderly over 60 years. The mental emptiness and physical diseases caused by the "empty nest" in elderly populations are the main factors of suicide 22,23 . Furthermore, elderly individuals generally exhibit poor health, more comorbidities 21 and poor prognosis, resulting in higher mortality 24 . We should take comprehensive preventive measures with the participation of the whole society and coordination of various departments to strengthen health education, psychological counselling and scientific propaganda of first aid for poisoning and focus on prevention and education of high-risk groups of suicide.
Most cities in southern Jiangsu are coastal cities, and the transportation industry is more developed compared with that in northern Jiangsu. Agriculture is also an important reason for the economic disparity between northern and southern of Jiangsu Province. Most of the reported cases of pesticide poisoning in Jiangsu Province from 2007 to 2016 occurred in the north and particularly included women and elderly individuals. This information is related to the development of industry and agriculture and the low economic level in northern Jiangsu. The reason may be that in the economically underdeveloped northern Jiangsu, women and the elderly are mostly engaged in agricultural work. Pesticide poisoning not only represents a large economic burden and psychological pressure to farmers but also a waste of medical and health resources and human resources. The government and relevant departments should increase their economic input to publicize measures for the prevention and control of pesticide poisoning.
The advantage of this research is that it includes pesticide poisoning cases from Jiangsu Province regardless of age. Many studies have focused exclusively on middle-aged individuals and paid little attention to pesticide poisoning in children and the elderly. In addition, this study focused on the incidence of pesticide poisoning in Jiangsu Province in the past decade, and the number of cases is relatively large and representative. The limitation of this study is that the number of pesticide poisoning cases is potentially underestimated.
The development of highly effective and low-toxic pesticides should be encouraged. Moreover, the population should be educated on safe production and use of pesticides, detoxification knowledge and personal protection capabilities [9][10][11][12]24 . Organophosphorus pesticides are the most commonly used drugs for suicide via oral ingestion and are the focus of suicide prevention. It is necessary to strengthen the knowledge of emergency rescue workers in primary medical institutions on pesticide poisoning. Moreover, government departments should regularly provide mental health education.
In summary, this paper described the situation of pesticide poisoning in Jiangsu Province from 2007 to 2016. The results indicated that the situation of non-occupational pesticide poisoning in Jiangsu Province remains grim, especially for intentional pesticide poisoning, which causes high mortality in elderly individuals. More measures should be taken to protect individuals from pesticide poisoning.

ethics.
All the informational data used in our study were encrypted and obtained from the official pesticide poisoning statistics and the ODSRS by the Jiangsu Provincial Centre for Disease Control and Prevention (JSCDC), China. The private information related to pesticide poisoning was encrypted. Our study complied with the Declaration of Helsinki and was exempted from institutional ethical review by the Research Ethics Board of JSCDC.
Data source. The pesticide poisoning data were mainly obtained from the ODSRS in Jiangsu Province from January 1, 2007 to December 31, 2016. The ODSRS includes data collected from hospitals, community health service centres, and clinical institutions. The data is entered into an online centralized system. According to the requirements of the system report, after receiving and treating the pesticide poisoning patients at all levels of health institutions, the attending physicians should complete the report card of pesticide poisoning and report the incident through the network within the prescribed time. Per the information included in the pesticide poisoning report card, sex, age, region, poisoned pesticide name, poisoning date, application method, diagnostic institution, poisoning reason, and date of diagnosis of the pesticide poisoning patient should be collected. the collected data is limited and does not include treatment and only reports a qualitative description of recover, improvement or death. statistical analysis. The data of pesticide poisoning in Jiangsu Province from 2007 to 2016 were introduced into EXCEL 2007 for sorting, and GraphPad Prim 5 was used for plotting. Data management and analysis were performed using SPSS 20.0. Qualitative data were described by relative numbers. The mortality of pesticide poisoning population was analysed using the chi-square test to determine significant differences between two or more groups. P-values < 0.05 signified statistical significance.

Data Availability
Data supporting the findings of the current study are available from the corresponding author on reasonable request.