1. IntroductionA five-year (2013–2017) survey of employed persons found that those with neither protection nor social security according to labour law were mainly working in the informal sectors. They had only received universal health coverage from the Thai government for health prevention and control, with no coverage regarding workers’ health compensation. In 2018, informal workers comprised 55.3% of the 38.3 million employed persons. They were primarily working in the north-east of Thailand. The majority of this group were farming workers or agriculturists (55.5%) who were mainly farm owners and subsistence farmers [1]. According to the agricultural census, which is conducted every 10 years, most recently in 2013, there were nearly six million registered farmers with holdings nationally. Regarding the agricultural holdings, about 96 percent were cultivating crops, while others involved rearing livestock, freshwater culturing, or sea salt farming. Thailand’s main crop is rice, but off-season crops such as cassava, sugarcane, rubber, and corn are grown in rotation, depending on the climate, soil, and water resources. Nearly half of the agricultural holdings can be found in the north-eastern region of Thailand (46.5%). Roi-Et and Udon Thani are two of the provinces among the top five provinces engaged in cultivating activities in the north-east of Thailand (comprising more than 97.0% of agricultural holdings) [2].Agriculture is an essential source of livelihood for developing countries. However, it can lead to poor health and is linked to the main causes of death and disease: malnutrition, infection, chronic diseases, and cancer [3]. In Thailand, various research studies have shown that agriculturists have a risk or chance of being exposed to health hazards that affect their health. The highest health risk found among cultivating rice farmers was pesticide toxicity [4], followed by work-related musculoskeletal disorders (WMSDs) [5], heat-related illnesses [6], and skin irritation (71.5%) [7]. The incidence of infectious diseases among cultivating farmers in Chonburi and Kamphaeng Phet provinces has been reported in previous studies as 83 cases of melioidosis [8] and 69 confirmed cases of leptospirosis [9]. During 2012 to 2016, infectious diseases, including leptospirosis and melioidosis, and plant and animal toxicity resulted in high morbidity rates among crop farmers in Nong Bua Lamphu province of Thailand [10]. The highest prevalence of work-related disease among agricultural workers has been WMSDs, followed by heat-related illnesses, i.e., heat or skin rash, heat stroke, sunburn, acne aestivalis, polymorphous light eruption, photo-aggravated dermatoses, and skin cancer from excessive sun exposure, pesticide toxicity, and skin irritation [11]. Some of the diseases are unclear in that they might not have been reported as occupational disease. Some diseases were not reported correctly by the clinic or hospital in relation to ICD-10.International Statistical Classification of Diseases and Related Health Problems: 10th Revision (ICD-10) codes have been used to specify diseases in Thai health databases. All occupational diseases are specified using Y96 as an additional code of a recorded ICD-10 disease to denote work as the external cause [12,13]. In 2012, the Department of Disease Control assigned specific clinics for agriculturists in primary care units (PCUs) to support health clinics in using the disease surveillance system of farmers in agricultural areas. Up until the time of this study, no reinforcement of the policy had been observed and occupational diseases with external cause coding have been largely ignored [14]. Subsequently, occupational diseases among farmers have rarely been reported, according to the disease surveillance on the Health Data Centre database in Thailand.A previous study showed that farmers tended not to report their occupation as agriculturists. The number of agriculturists in the health database within the PCUs are not a true representation of the population, as shown in the previous report by Chaiklieng et al. [15]. The Provincial Agriculture Office can provide more accurate data on the actual number of people working in the agricultural sector. These databases include registered farmers so they can access benefits and support from the government. An investigation into the incidence of diseases and occupational injuries among farmers who were actually registered and had morbidity reports in the Health Data Centre (HDC) database found no study findings from 2014–2016 [15] consistent with the ostensible increase in pesticides imported to Thailand in 2013 [16]. The HDC is the central health database system of Thailand that collects and analyses the disease surveillance system data of all healthcare services under the provincial public health office by using 43 files, or standard structured data, classified with ICD-10 codes for diseases and disorders, and records the patient’s information every time they receive services from officials. However, previous reports have found a high prevalence of work-related diseases and injuries in a systematic review [11] and included occupational diseases from the HDC [17].

This study investigated the incidence rate of work-related diseases and injuries among farmers who were registered with the Provincial Agriculture Office in two provinces in the north-east of Thailand: Udon Thani and Roi-Et. This study retrospectively retrieved data on incidences of diseases and injuries among farmers between 2014 and 2016. We also looked at other occupational-related diseases that had not previously been reported as occupational diseases within the ICD-10 classification, such as lung disease, skin disease, and infectious disease. We also included diseases that were due to toxicity exposure or chemicals other than pesticides, including solvents, metals and gases, fumes, and vapours.

4. DiscussionThe study found that the highest morbidity rates of occupational diseases in a three-year period (2014–2016), in descending order, were WMSDs, infectious disease, skin disease, and lung disease. This confirms the results of a previous study which found that WMSDs had the highest morbidity rate among field crop farmers [10] and is consistent with the WMSD prevalence among farmers in Pathum Thani, Thailand [18]. In the surveillance report of the morbidity rates of occupational and environmental diseases in 2018, it was found that WMSDs had a morbidity rate of 189.37 per 100,000 persons of the Thai population [17]. Although the morbidity rate of WMSDs in this study, about 50,000 per 100,000 farmers, seems to be much higher than that of the surveillance report of the general Thai population, it strongly points toward being specific to the adverse health problems of cultivating farmers. In addition, the morbidity rate of about 50% is consistent with our previous meta-analysis which showed that WMSDs are the most prevalent occupational health problem among Thai agriculturists [11].The morbidity rate for WMSDs in Roi-Et is higher than Udon Thani province, according to data from the most current year, 2020 [19]. The WMSDs ICD-10 codes in Table 1 were categorized in Thailand’s surveillance system, but they only allow for the knowledge of disease incidence rates and cannot be used to identify the organs that are affected in WMSDs [19]. The previous study showed different types of cultivation led to pain in different body regions. The results showed that the workers on rubber plantations were more likely to feel knee/calf pain (OR = 1.59, 95% CI = 1.05–2.39) and lower limb pain (OR = 1.97, 95% CI = 1.35–2.89) than those who were working on rice and tobacco plantations [20]. These results could explain the higher rate in Roi-Et, where there were more rubber planting farmers in this study than in Udon Thani.Infectious disease had the second highest incidence among all diseases, which has not yet been observed in the surveillance report of health data on the groups of occupational disease in Thailand [18]. Previous analysis of the health data files of Thai crop farmers found that infectious diseases were in the top three most severe diseases from the high case fatality rate [10]. Leptospirosis, melioidosis, and toxicity from plants and diseases from contact with animals were previously reported in crop farmers [10]. In the same way, it was found that workers were exposed to diseases from contact with animals and plant poisoning as much as they received injuries in the field. This was not only the case in Thailand; a previous study in Poland [21], which corresponded to annual reports in Greece [22], also reported a high incidence of infectious diseases.However, with regard to the high morbidity rate of injuries, it was not certain whether such injuries occurred during work on farms because the external code specific to the workplace was missing. A previous study showed that insufficient primary healthcare personnel [23] and their lack of understanding with regard to coding occupational disease into the hospital information system with ICD-10 codes during the provision of routine services in the primary care units (PCUs) [14] were an issue. However, in recent years, the proportion of people with easy access to hospital treatment or treatment at PCUs was indicated as 68.55% of the Thai population [24], and the proportion of people accessing the health service had not increased much from the previous years. Therefore, the high incidence of occupational diseases found in this study could not be explained by the reason that health services had become more accessible. Moreover, the total number of cases among registered farmers visiting PCUs or hospitals for healthcare services in Udon Thani was lower than that of Roi-Et province and was far lower than the national rate.At present, cultivating agriculturists have chances to be exposed to noise and gases, and fumes and vapours from agricultural machinery (water pumps, combine harvesters, and tractors) which is often used as power-saving machinery on farms [25]. This study found that morbidity rates of hearing loss, heat illnesses, and air pressure effects in Udon Thani province were higher than those of Roi-Et province although the number of registered agriculturists of Roi-Et was higher than that of Udon Thani province [2]. Another previous study showed that agriculturists who had work experience with noise exposure was correlated significantly with hearing loss [26]. It is possible that the high morbidity rate of hearing loss in Udon Thani was related with the fact that the number of factories and workers in the industrial sector was higher than in Roi-Et province [26].In the same way as that of physical hazards, the incidence of pesticide toxicity in Udon Thani province was higher than that of Roi-Et province but not as high as that of other disorders. Pesticide toxicity has been shown to be a potential disease of the agricultural sector of Thailand, and there was a trend of increasing pesticide imports, particularly herbicide imports, during a 5-year period from 2013 to 2017 [16]. The ICD-10 records of pesticide poisoning on the health surveillance system were only coded in the T60 group, as presented in this study, which showed the morbidity rate was underrepresented but likely higher than the rate of the Thai adult population in 2019 (13–17 cases per 100,000 a year) [27]. The previous study of pesticide poisoning reports among farmers showed incomplete records for the secondary codes Y96 and Y97 as well as the external cause X48 which were found in 45.14% and 17.84% of cases, respectively [14]. Moreover, there were key concerns regarding public health personnel being responsible for multiple tasks, without any understanding of pesticide poisoning disease codes, and never having received training for occupational disease recording [14].However, the acute effects of pesticides could possibly be skin health effects, e.g., infective dermatitis (L303), and lung health effects, e.g., respiratory symptoms due to inhalation of chemicals, including gases and vapours (J68) [28]. This study found that skin and lung diseases had the third and fourth highest morbidity rates of occupational diseases, which might be affected by exposure to all forms of chemicals. Moreover, a previous study in Roi-Et province found that ICD-10 identification and reports on the disease surveillance system with external code Y96 (work-related condition) were missing, as were reports in severe cases of pesticide poisoning with T-toxicity coding [14,28]. Therefore, pesticide toxicity was shown to be underestimated in regard to occupation, particularly that of cultivating farmer. Thailand’s public health policy should include ICD-10 code L (skin disease) and code J (lung diseases) to identify the acute and chronic effects of pesticide toxicity among applicators, as found in the previous case-control study of Thai cultivating farmers in Sakon Nakhon province on pesticide toxicity [28].Regarding agricultural productivity in the study area, the Office of Agricultural Economics reports cassava, rubber, and rice had the highest productivity between 2016 and 2019 [29]. In comparison to Roi-Et province, Udon Thani province has almost five times the production areas of cassava and Para rubber [29]. This study reveals that Udon Thani has a higher morbidity rate for pesticide poisoning than Roi-Et province. Hence, it is clear that paraquat or glyphosate herbicide must be used continuously to treat the rubber and cassava while it is being harvested. This hypothesis was confirmed by previous study that the morbidity rate of pesticide toxicity by ICD-10 identification was highest in farmers who grew cassava and rubber, respectively [10]. Most intriguingly, it was found that between the years 2014 and 2016, the province of Roi-Et had the fourth-highest tonnage of inland rice production in the country [29]. In comparison to the province of Udon Thani, Roi-Et’s in-season rice yield was approximately 2–3 times more productive [29]. This study discovered that the incidence of WMSDs in Roi-Et was also greater than in Udon Thani province, presumably because rice farming requires body exertion in various agricultural activities throughout the year more than farming of other crops, e.g., cassava farming. Moreover, previous study showed that farmers had higher MSDs prevalence rates than the non-farmer in the case-control and cohort studies [30].This study has the strength of using big data of health from two provincial databases, as previously mentioned, to give a representation of farmers engaged in agricultural activities. Furthermore, the identified cases are linked to the entire farmer population. Although only two provinces were studied, the nature of the impact from agricultural work was found to be not much different from that of other areas. The higher rate of occupational diseases specific to a more cultivating-agriculture-based province, Roi-Et, than that of Udon Thani, from the observation of the five most common health problems, i.e., WMSDs, injuries, and infectious, skin, and lung diseases, could confirm our previous report from the meta-analysis of the occupational disease situation in Thailand [11]. However, this study was conducted prior to legislation of Thailand’s Occupational Diseases and Environmental Diseases Control Act B.E. 2562 (2019), which suggests that healthcare providers identify occupational diseases through surveillance. Future research should compare the findings of this study to epidemiological studies currently being conducted among Thai agriculturists. 5. Conclusions

This three-year retrospective cohort study aimed to investigate the incidence of work-related diseases and injuries among cultivating farmers of Roi-Et and Udon Thani provinces, Thailand. The study was conducted among groups of 207,465 and 154,478 cultivating farmers of Roi-Et and Udon Thani provinces, respectively. There were 53,794 (34.82%) total cases who visited PCUs or hospitals for health services in Udon Thani, and 77,438 (37.32%) total cases in Roi-Et. The highest incidence rate was that of work-related musculoskeletal disorders (WMSDs), followed by injuries, infectious disease, skin disease, and lung disease, respectively. All of those effects had a higher rate in Roi-Et province, a more cultivating-agriculture-based province, than in Udon Thani province. These representative morbidity rates confirmed the high incidence of WMSDs and injuries, which are common work-related health problems of workers. Moreover, infectious, lung, and skin diseases were discovered in cultivating farmers. Therefore, the representative incidence of diseases obtained by using big data analysis of the health problems among registered agriculturists could be used to represent the real situation for strategic planning of occupational health services and prevention of diseases by a priority health surveillance program.