Occupational exposure to pesticides can occur mainly in factory workers during manufacturing and in farmers during mixing/loading, spraying, and harvesting the agricultural commodities. Acute and chronic health threats of pesticide exposure greatly concern farmers, which arise from the amount and frequency of pesticide use, the time farmers spend in their fields, and the potential unsafe exposure levels in these situations. To deal with concerns about pesticide hazards, their exposure should be appropriately controlled to ensure the health of agricultural workers.
Following pesticide application to agricultural crops, its exposure is primarily attributed to dermal deposition and inhalation. Dermal deposition/adsorption is the main route of exposure to farmers and occurs indirectly through contact between the skin and the leaf surface stained with the spraying solution, but not through direct contact with the pesticide droplet after application . Dislodgeable foliar residues (DFRs) of pesticides can easily translocate to the body surface of workers during pesticide application, pruning, thinning, and harvesting . Therefore, a dissipation study of DFRs was conducted to predict the dermal exposure of farm workers to pesticide and determine the safe reentry interval (REI). Transfer factor (TF) can be considered a link between dermal exposure rates (DERs) and DFRs . TF is the ratio of exposure to the DFRs and calculated using DERs and the foliage surface area contacted by the worker per hour [4, 5]. Consequently, the estimation of dermal exposure to other pesticides is possible using specific TF values established for specific crops, activities, and field conditions .
The number of greenhouse farms and the cultivation area have increased globally, particularly in Korea, because of the high production capacities per unit area and year-round cultivation. In 2020, greenhouse acreage and production reached 60,866 hectares and 2.3 million tons, respectively, in the Republic of Korea . Moreover, farm workers frequently reenter the facility for the continuous harvesting of agricultural commodities such as cucumber, which has grown 87% of the total production in the greenhouse. As a result, the probability of farmworker exposure to pesticides also increased in specific work tasks, which could be attributed to the enclosed greenhouse farm system, frequent pesticide application and reentry. The resultant health effects among greenhouse farm workers have continued to be reported, including hormonal, neurological, and respiratory disorders [8,9,10,11].
In Korea, exposure to mixers and sprayers during pesticide application has been a great deal of focus in the past [1, 12,13,14]. The exposure characteristics for applicators were reported in open fields, including green pepper fields, paddy fields, mandarin, and apple orchards [1, 12, 13], and were also compared by diverse formulations and different application methods [1, 13]. Moreover, the exposure pattern for agricultural workers was investigated during the application of the pesticide suspension to the cucumber in a greenhouse environment [1, 14]. However, there is also the possibility of exposure in a field sprayed previously with pesticides, where agricultural workers reenter for picking, harvesting, pruning/thinning, maintenance, etc. In Korea’s farming situation, agricultural workers generally prefer to wear long-sleeved shirts and long trousers instead of personal protective equipment (PPE) during the harvest, because of the inconvenience of the work, thereby causing a higher possibility of risk to pesticides [15, 16]. My research group previously reported the exposure and risk to methidation for workers during harvesting cucumber for 7 days in the greenhouse, which showed that workers exposed mainly through hands, thighs, and arms by the direct contact with the pesticides on crop foliage or cucumber . Besides, the deposition and dissipation characteristics of methidathion on cucumber foliage were also investigated in my previous publication .
As mentioned above, exposure to reentering workers could be estimated using the TF value calculated from the DERs and DFRs. To the best of my knowledge, no previous reports on the DERs for harvesters and DFRs have been published in the Republic of Korea, except for my previous papers. Hence, this study aimed to derive the TF value using reentry DERs and DFRs measured concurrently in the same cucumber greenhouse, reported in my previous works [17, 18]. In addition, the REIs of 82 pesticides registered on cucumber were determined to set priorities for pesticide exposure management.