Pesticide Application, Dermal Exposure Risk and Factors Influencing Distribution on Different Body Parts Among Agriculture Workers
Key Findings
- Dermal contact is the most common route of pesticide exposure among agricultural workers, typically occurring during mixing, loading, application, and harvesting
- Exposure rates are influenced by application equipment, application rate and duration, pesticide formulation type, PPE use, and environmental conditions
- Pesticide type was not a major factor in determining total dermal exposure; rather, application method and protective measures were more determinant
- Malaysia’s diverse agriculture subsectors (palm oil, paddy, vegetables, rubber) present varied dermal exposure profiles requiring tailored prevention strategies
Background
The agricultural sector remains one of the most hazardous industries globally, with pesticide exposure representing a principal occupational health risk for farming communities. According to the World Health Organization, an estimated 385 million cases of unintentional acute pesticide poisoning occur annually worldwide, with the vast majority affecting agricultural workers in developing countries. Malaysia, with its robust agricultural sector contributing significantly to national GDP through palm oil, rubber, paddy rice, and horticultural crop production, employs substantial numbers of workers who are regularly exposed to pesticides.
Among the three primary routes of pesticide entry into the body—dermal, inhalation, and oral—dermal absorption is consistently identified as the dominant pathway for occupational exposure. Skin contact with pesticides can occur at multiple stages of the agricultural process, including preparation of spray mixtures, application in the field, cleaning of equipment, and harvesting of treated crops. Despite the recognition that dermal exposure is the predominant route, the factors that influence how pesticides distribute across different body regions have not been comprehensively reviewed, particularly in the context of Malaysian agriculture.
This review article examined the current knowledge on pesticide dermal exposure risk assessment methods, the factors that influence exposure levels, and the distribution patterns of pesticide contamination across different body parts among agriculture workers.
Pesticide Management Activities and Exposure Routes
The review framework examined pesticide exposure through the lens of three key management activities: preparation, application, and cleaning. Each stage presents distinct exposure risks through three corresponding routes: emission (release of pesticide into the environment), deposition (settling of pesticide onto surfaces including skin), and transfer (movement of deposited pesticide from contaminated surfaces to the body).
Preparation Stage
During pesticide preparation—which includes measuring, mixing, and loading products into application equipment—workers are at high risk of dermal exposure, particularly to the hands and forearms. Concentrated formulations handled at this stage can pose greater hazards per unit exposure than diluted field applications. Spillage during transfer between containers and splashing during mixing are common exposure events.
Application Stage
The application phase typically represents the longest duration of potential exposure and involves the greatest body surface area at risk. Factors influencing exposure during application include the type of spray equipment (knapsack sprayers, motorised sprayers, tractor-mounted systems), nozzle characteristics, walking direction relative to spray drift, plant height and canopy density, and ambient weather conditions including wind speed, temperature, and humidity.
Cleaning Stage
Post-application cleaning of equipment and personal decontamination represents an often-overlooked exposure opportunity. Inadequate cleaning of spray equipment can lead to residual pesticide exposure during subsequent handling, while insufficient personal hygiene after application extends the duration of skin contact with deposited pesticides.
Dermal Exposure Risk Assessment Methods
The review discussed two main categories of risk assessment: exposure assessment and effect assessment. Exposure assessment methods include the whole body dosimetry technique (using absorbent pads placed on different body regions beneath clothing to quantify deposition), fluorescent tracer methods (using UV-visible tracers to visualise and quantify contamination patterns), biological monitoring (measuring pesticide metabolites in blood or urine), and semi-quantitative observational tools such as the Dermal Exposure Assessment Method (DREAM).
Factors Influencing Exposure Distribution
The review identified several key factors that determine how pesticide exposure distributes across the body:
| Factor | Influence on Exposure Distribution |
|---|---|
| Application equipment | Knapsack sprayers concentrate exposure on the back, legs, and forearms; motorised sprayers shift exposure to front body regions |
| Application rate and duration | Higher spray rates and longer application periods increase total body exposure proportionally |
| Pesticide formulation type | Liquid concentrates pose higher splash risk; granular formulations affect hands predominantly |
| Personal protective equipment | Appropriate PPE dramatically reduces exposure to covered body regions but compliance is often poor |
| Plant height and canopy | Taller crops redirect spray onto upper body regions; low crops concentrate exposure on lower extremities |
| Environmental conditions | Wind increases spray drift; high temperature and humidity affect skin absorption rates |
Malaysian Agricultural Context
The review highlighted that Malaysia’s diverse agricultural subsectors present varying exposure profiles. Palm oil plantation workers face distinct exposure patterns compared to paddy farmers or vegetable growers, due to differences in crop architecture, application methods, and pesticide types used. Research conducted in Malaysia has shown that compliance with personal protective equipment recommendations is notably low, with one study finding that only 8.4% of paddy farmers in Tanjung Karang wore proper PPE during pesticide application.
The predominantly tropical climate of Malaysia adds further complexity to dermal exposure assessment, as high ambient temperatures promote perspiration that can enhance dermal absorption of many pesticide formulations, while also reducing worker compliance with protective clothing due to heat stress.
Public Health Implications
This comprehensive review provides a foundation for developing evidence-based guidelines for pesticide safety in Malaysian agriculture. Key recommendations include strengthening PPE compliance through education and provision of heat-adapted protective equipment suitable for tropical conditions; implementing exposure monitoring programmes across different agricultural subsectors; and developing standardised training materials for pesticide handlers that address the specific exposure patterns identified for each type of farming activity.
Regulatory agencies such as the Department of Occupational Safety and Health and the Department of Agriculture should leverage this evidence base to update pesticide handling guidelines and enforce exposure limits that reflect the dermal route as the primary pathway. Integration of dermal exposure assessment into occupational health surveillance programmes for agricultural workers would enable early detection of overexposure and more targeted intervention strategies.
Limitations
As a review article, this paper is dependent on the quality and scope of the primary studies it examines. Much of the published literature on pesticide dermal exposure originates from temperate-climate developed nations, and findings may not fully translate to tropical agricultural settings in Malaysia. The review noted the limited number of Malaysian-specific dermal exposure studies available at the time of publication, particularly for smaller-scale farming operations and non-plantation agriculture. Quantitative synthesis (meta-analysis) was not performed due to heterogeneity in study designs and measurement methods across the reviewed literature.
Pesticide Application, Dermal Exposure Risk and Factors Influenced Distribution on Different Body Parts Among Agriculture Workers. Malaysian Journal of Public Health Medicine. 2017; Special Volume (1).
License: Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)