The association between health literacy and pesticide use behaviors among sweet corn farmers in the Pak Chong district of Thailand: a cross-sectional study

Introduction

Agricultural production accounts for 10% of the Kingdom of Thailand’s gross domestic product (GDP) and 60% of employment. As in many developing countries, in order to achieve high yields, farmers in Thailand use pesticides and herbicides to control pests, weeds and other pathogens. Despite following stricter regulations, increasing evidence of the health risks associated with exposure to pesticides and pesticide residues contaminating food, water and air^1,2, imports of insecticides, herbicides, and fungicides have peaked in the last decade, particularly between 2011 to 2017³. The top ten pesticides imported by Thailand are glyphosate, paraquat, 2,4-D-dimethylammonium, atrazine, ametryn, 2,4-D-sodium, diuron, propyl, chlorpyrifos, and mancozeb⁴. The World Health Organization (WHO) classification of pesticides by hazard has been aligned with the GHS (The Globally Harmonized System of Classification and Labelling of Chemicals) acute toxicity hazard categories: Ia = extremely hazardous; Ib = highly hazardous; II = moderately hazardous; III = slightly hazardous; U = unlikely to present an acute hazard; O = Obsolete as pesticide (not classified)³. Those pesticides classified as toxic include glyphosate (III), paraquat (II), 2,4-D-dimethylammonium (II), atrazine (III), ametryn (II), 2,4-D-sodium, diuron (III), propyl (O), chlorpyrifos (II), and mancozeb (U). Currently, the Thai Pesticide Alert Network (Thai-PAN) is campaigning and working with the government of Thailand to ban four pesticides (paraquat, glyphosate, chlorpyrifos, and 2,4D) due to their long-term health effects on humans. In addition, Thailand has adopted the Sufficiency Economy Philosophy as a guideline for agriculture. According to this philosophy, building immunity to environmental changes prompts individuals and their communities to be aware of the impacts their actions may have on the environment and, subsequently, their livelihoods, an awareness which leads them to live in harmony with nature⁵. The environmental aspects of this guideline enable people and communities to realize the effects of pesticides on health, environment and livelihoods.

However, pesticide use trends indicate that pesticide use is increasing⁶. Although pesticides are beneficial for the control of pests, there are serious concerns for humans and animals regarding associated health risks. Pesticides are chemicals which have been designed to be toxic to pests and, in many cases, their toxic nature can also be harmful to human health^1,7,8 and cause environmental pollution⁹. There have been reports of strong associations between exposure to pesticides and cancer¹⁰, and studies have shown that the exposure of pregnant women and breastfeeding mothers to pesticides is a risk factor for low birth weight, congenital birth defects, growth defects, learning disabilities and miscarriage^1,11. Previous evidence suggests that farmers have awareness and a basic understanding of insecticides, pesticides and various other chemicals used in farming practices^12–14 However, this awareness and knowledge alone might not lead to reduced use of the various chemicals when farming. Health literacy (HL) is a relatively new concept for social and medical sciences research. HL is the ability of individuals to understand basic health information and gain access to essential services, thereby enabling them to make informed decisions^9,10. Health literacy can be separated into three levels^15–17: (1) Functional literacy, which focuses on the ability to read, understand and access pesticide information; (2) Interactive literacy, which involves the use of cognitive skills and operates in a social environment that supports social participation in health-related issues in the community; (3) Critical literacy, which is the ability to evaluate health issues and determine the challenges of these issues.

The patterns of pesticide use were studied in three phases of sweet corn farming: pre-planting, pre-emergence and post-emergence. Sweet corn farmers use various methods when applying pesticide such as mixing, loading, spraying and washing equipment. Mixing involves weighing or measuring the pesticide in some fashion and mixing the measured concentrated product with a diluent. Loading involves pouring the diluted pesticide into the spray equipment. Spraying involves the application of the pesticide to control pests by spraying. This is the most common activity for farmers. Typical equipment used may be backpack sprayers or hand-held tank sprayers. Washing involves cleaning the equipment used for pesticide application which may be contaminated during the spraying operation. Pesticide use patterns included the number, type, toxicity and concentration of pesticides used and pesticide use behaviors. There are very few studies about pesticide use among sweet corn farmers. The aim of this research was to determine and discuss patterns of pesticide use, HL of pesticides used, pesticide use behaviors and the association between HL and the behaviors of sweet corn farmers.

Methods

This research applied a cross-sectional, quantitative design to identify determinants of health literacy and pesticide use. This study was carried out from May 2017 to July 2017. The participants were sweet corn farmers in the Pak Chong district of Nakhon Ratchasima province, Thailand. Specifically, the study was conducted in the Klangdong, Chanthuek, Wang Sai and Mu Si sub-districts of the Pak Chong district as these are the regions in which sweet corn is grown. Within these regions, 194 sweet corn farmers were identified through visits to the farms in the area. However, 33 farmers were unwilling to be interviewed.

The research framework was approved by the ethical committee of Khon Kaen University, Thailand (HE601107). The eligibility criteria of the respondents include sweet corn farmers who live in Pak Chong district, who had used a pesticide for at least 6 months, who could read and write and who were willing to participate in the study. Written informed consent was obtained from all the participants (n = 161). Interviews were conducted by the author (T.P.) using a questionnaire, which included questions about socio-demographic factors and patterns of pesticide use, and answers from farmers were given orally. In order to assess health literacy, the three levels were further separated into 6 dimensions: cognitive skills, access, communication skills, self-management, media literacy and decision-making skills. Cognitive skills refers to the knowledge and understanding the participant has about the correct use of pesticides. Access refers to the access the participant has to pesticide effect information and health services. Communication skills refers to the ability of the participant to listen, speak, read and write about pesticide use. Self-management refers to the ability of the participant to protect their health and reduce the impact on the environment of pesticide application. Media literacy refers to the ability to compare information regarding pesticide efficacy from media such as newspapers, radio, television and pesticide advertisements. Decision-making skills refers to the ability of the participant to decide what pesticides to use and how to use them in a way that does not have a negative impact on their health or the environment.

Three experts from Thai-PAN (Thai Pesticide Alert Network) verified the content validity. The consistency index for all items was 0.61. A pilot test (sample size of 30) was used to achieve clarity for the questionnaires. Cronbach’s alpha, a measure of internal consistency, was 0.72 for the HL of pesticide use section of the questionnaire and 0.77 for the pesticide use behaviors section. Responses to questions 1–10 (cognitive skills) were marked as correct or incorrect. Responses to the remaining questions were scored qualitatively, using a 5-point Likert scale. The item responses ranged from 1 (very low) to 5 (very high). The HL of pesticide use section was composed of 36 items and it was separated into 6 parts (access, cognitive skills, communication skills, self-management, media literacy and decision-making skills). Responses to the 36 items were scored as low, moderate or high levels of health literacy for pesticide use. The maximum score for health literacy was 135. A score of <81 was considered to be low, a score of 81–108 was considered to be moderate and a score of >107 was considered to be high. A breakdown of the score thresholds for each dimension and level of health literacy can be found in Table 1. The pesticide use behaviors section was composed of 20 items, divided into 3 parts (before application, pesticide application and after application). Responses to the 20 items were scored as low, moderate and high standards of pesticide use behaviors. The maximum score for pesticide use behaviors was 100. A score of <67 was considered to be low, a score of 67–69 was considered to be moderate and a score of >69 was considered to be high. A breakdown of the score thresholds for each phase of pesticide application can be found in Table 2.

Descriptive statistics, such as frequencies, percentage, mean and standard deviation (S.D.) are used to report the socio-demographic factors, number of years using pesticides, number of annual pesticide applications, total types of pesticide used in pre-planting, pre-emergence and post-emergence phases of sweet corn farming. In addition, pesticide use behaviors such as; the type of pesticides, the level of toxicity of pesticides and the concentration of pesticides are reported using descriptive statistics. The Chi-squared test was used to test the association between HL and pesticide use behaviors using SPSS (version 20). This analysis could also be performed using a non-proprietary software such as R.

Results

Discussion

Findings of patterns of pesticide use, health literacy and pesticide use behaviors suggest that it is necessary to reduce the harmful effects of pesticide use. Findings included (1) the majority of sweet corn farmers did not follow the current recommended dose or number of sprays, (2) there are many pesticides used in the planting of sweet corn, (3) pesticides used in growing sweet corn have moderate toxicity and (4) the pesticide use behaviors during all phases of planting are unsafe¹⁸. However, assessing the risk of exposure to pesticides for humans is not easy because of differences in the duration and levels of exposure to the substance^2,7. In addition, the level of HL of the farmers was moderate. Based on these findings, pesticide use by these farmers may affect environmental health^8,9 and lead to the pollution of soil and water (surface and groundwater) and diseases of humans¹⁹.

Therefore, training sweet corn farmers to reduce the use of pesticides^20,21 through an intervention program may be necessary to improve farmer safety. These findings are also consistent with previous studies^22,23 regarding health literacy (HL) and pesticide use behaviors. When the sweet corn farmers have knowledge of the pesticide being used, they may have more appropriate pesticide use behaviors. This leads to the suggestion of developing guidelines for appropriate pesticide use for each plant, following a study of the types of pesticides used for each species.

Developing HL of the risks of pesticide use requires effective communication in order to lead to an improvement in pesticide use by sweet corn farmers, which could lead to the improvement in health in this century²⁴. There are a number of ways to reduce the harmful effects of pesticide use. (1) Education for farmers about how to use PPE^17,21,25 with a focus on apron, mask and wide-brimmed hat use because the relative absorption rate of pesticides is highest in the genital area, ear canal, forehead and scalp (11.8% 5.4% 4.2% and 3.7%)²⁶. Moreover, product labels should be developed that are easy to understand. (2) Promote the use of PPE while mixing, loading and applying any pesticides, especially aprons and goggles or face shields. (3) Behavior such as eating, drinking water or alcohol and smoking should not be undertaken in areas where spraying of pesticides is necessary because the body can absorb the pesticides. (4) Farmers should take a bath at the farm to avoid contaminating family or close friends²⁷. However, farmers cannot bathe in the immediate area where they use pesticides. There are two ways to do this: use a water jug for bathing or change clothes immediately before returning home, separating the pesticide-contaminated clothing from other clothes. (5) Sweet corn planting farmers use up to nine pesticides, seven of which belong to toxicity class II according to the WHO, including 2-4D, glyphosate and atrazine that likely cause cancer¹⁴. Sweet corn farmers should be careful with pesticide use, should have access to information regarding pesticide toxicity and should be encouraged to switch to organic farming methods. (6) The harm reduction principle should be applied to promote a reduction in the number of pesticides used, reduce the use of especially toxic pesticides and promote the use of the recommended pesticide concentrations. This would help to protect sweet corn farmers, others indirectly exposed to the pesticides, consumers and the environment. However, promoting the use of organic farming might be rejected by farmers as some sweet corn farmers prefer to use unsuitable pesticides in order to ensure yield and quality²⁸.

Conclusions

The present study found that the health literacy of pesticide use in sweet corn farmers was at a moderate level and pesticide use behaviors were at a low level, with a tendency towards a high level of pesticide use behaviors. However, farmers had a moderate level of pesticide use behaviors at the ‘after pesticide application’ phase. This baseline study gives an insight into the range of pesticides used in the management of sweet corn pests and diseases in Thailand and found that 9 pesticides were used. The pesticides used in growing sweet corn have moderate toxicity. The major factors relating to pesticide use behaviors were the self-management and decision-making skills dimensions (p < 0.01). The lack of health literacy regarding pesticide calls for training for sweet corn farmers. To reduce the dependence on pesticides it is important to promote health literacy, especially in the cognitive skills, media skills and decision-making skills. The farmer has to find out what works best for them for reducing pesticide use when planting sweet corn. However, effective communication can lead to an improvement in pesticide use by farmers and may lead to improvements in environmental and ecological health.

Data availability