Organophosphate Pesticide Mixture Exposure: The Relationship with the Motor Coordination of Children from Paddy Farming Area in Tanjung Karang, Malaysia

Last reviewed: March 2026

Background and Rationale

Tanjung Karang, located in Selangor state, hosts the third largest paddy field in Malaysia and represents one of the country’s most important rice-producing regions. As with most intensive agricultural areas worldwide, paddy cultivation in Tanjung Karang relies heavily on pesticides to control pests and maximise yields. Organophosphate (OP) pesticides and carbamates are among the most commonly used insecticides in Malaysian rice farming, and their widespread application raises significant concerns about the health effects of environmental exposure, particularly among vulnerable populations such as children.

Organophosphate pesticides exert their toxic effects primarily through inhibition of acetylcholinesterase, an enzyme essential for normal nerve function. In adults, acute OP exposure can cause a range of neurological symptoms. In children, however, the consequences may be more insidious and long-lasting, as the developing nervous system is particularly susceptible to neurotoxic insults. A growing body of international evidence has linked chronic low-level OP exposure in children to impairments in cognitive function, attention, memory, and motor coordination.

This study, published in the Malaysian Journal of Public Health Medicine, was among the first to systematically investigate the neurodevelopmental effects of environmental OP exposure in Malaysian children living in an agricultural community. It builds on a body of work from Universiti Putra Malaysia that has established Tanjung Karang as a key site for studying the health impacts of agricultural pesticide use in Malaysia.

Study Design and Methods

The researchers conducted a cross-sectional study among 114 primary school children aged 10 to 11 years residing in Tanjung Karang. Participants were selected using random sampling from children who met the inclusion criteria: healthy, enrolled in local primary schools, and with parental written consent. A parent-completed questionnaire collected background information including residential proximity to paddy fields, children’s play behaviours, and exposure-related factors.

Blood cholinesterase concentration, used as a biomarker of organophosphate pesticide exposure, was measured from capillary blood samples obtained via finger prick technique. Analysis was performed using a rapid test cholinesterase test kit (Model LOVIBOND 412870 AF287), a field-appropriate instrument validated for community-based screening studies.

Neurodevelopmental assessment was conducted using all seven tests of the WHO Neurobehavioral Core Test Battery (NCTB), an internationally standardised battery designed to assess the effects of neurotoxic exposures on a range of cognitive and motor functions. The NCTB includes assessments of motor steadiness, eye-hand coordination, attention, response speed, and perceptual motor speed.

Principal Findings

The results painted a concerning picture of neurobehavioral function among children in this agricultural community. Mean scores were notably poor across several domains of the NCTB, with motor steadiness (assessed via the Trail Making Test) scoring particularly low at 36.61. Rapid coordination of eye and hand (assessed via the Time Reaction/Movement Test) also showed impaired performance, with a mean score of 46.17. Attention and response speed (47.28) and perceptual motor speed (47.38) also fell below expected norms.

Statistical analysis revealed significant correlations between blood cholinesterase levels and performance on two specific neurobehavioral tests. The Trail Making Test, which measures motor steadiness, showed a significant correlation with blood cholinesterase (p = 0.003), as did the Pursuit Aiming Test (p < 0.001). These correlations provide evidence that OP exposure, as reflected in reduced cholinesterase activity, was associated with measurable impairments in motor function among these children.

Environmental Predictors of Exposure

Further analysis examined the environmental and behavioural factors that predicted blood cholinesterase levels in this population. Two factors emerged as particularly significant: home proximity to the paddy fields (p < 0.001) and frequency of playing near paddy fields (p = 0.039). Children whose homes were located closer to the fields—particularly within 100 metres—had significantly lower cholinesterase levels, indicating greater OP exposure. Similarly, children who frequently played in or near paddy field areas showed evidence of higher pesticide exposure.

Trail Making Test scores (reflecting motor steadiness) were significantly related to the frequency of children playing near the paddy field (p = 0.039), while Time Reaction/Movement Test scores (reflecting rapid coordination of eye and hand) were significantly related to home location with respect to the paddy fields (p = 0.042). These findings underscore the role of residential proximity and outdoor play behaviour as key pathways through which children in agricultural communities are exposed to environmental pesticide contamination.

Context Within Malaysian Agricultural Health Research

This study contributes to a growing body of evidence from Tanjung Karang that has documented multiple health effects of pesticide exposure in this community. Related studies from the same research group have investigated blood cholinesterase levels and learning ability, neurobehavioral performance among paddy farmers themselves, and the presence of pesticide residues in local water sources. The Pesticide Action Network Asia Pacific (PANAP) has also highlighted Tanjung Karang in its studies on highly hazardous pesticides in the region, noting that more than half of surveyed farmers manifested symptoms of pesticide poisoning.

The cumulative evidence from Tanjung Karang paints a picture of a community where agricultural pesticide use has created measurable health risks for both farmers and their families, including children who are exposed through environmental contamination rather than direct occupational contact. This has implications not only for Tanjung Karang but for other agricultural communities across Malaysia and the broader ASEAN region.

Implications for Policy and Practice

The findings support several policy recommendations. First, there is a need for improved regulation and monitoring of pesticide use in agricultural areas, with particular attention to organophosphate compounds. Second, community education programmes should inform families about the risks of pesticide exposure to children, including the importance of limiting children’s play activities in or near treated fields. Third, consideration should be given to promoting safer, non-chemical alternatives to pesticide use, as advocated by PANAP and other environmental health organisations.

From a clinical perspective, regular health screening of children in agricultural communities—including neurodevelopmental assessment and biomarker monitoring—may help identify affected individuals early and facilitate appropriate interventions. Schools in agricultural areas could serve as important venues for such screening programmes.

Limitations

The cross-sectional design limits the ability to establish causal relationships between OP exposure and neurodevelopmental outcomes. The study did not include a comparison group of children from non-agricultural areas, which would have strengthened the evidence for a pesticide-specific effect. Blood cholinesterase, while a useful biomarker for OP exposure, is a non-specific indicator that can be influenced by other factors. The sample size of 114 children, while adequate for the correlational analyses performed, limited the ability to conduct more complex multivariate analyses that could have controlled for additional potential confounders.

Significance of This Research

This study provides important evidence that environmental organophosphate pesticide exposure in Malaysian agricultural communities is associated with measurable impairments in children’s motor coordination and neurobehavioral function. It highlights the particular vulnerability of children who live near and play around pesticide-treated areas, and underscores the need for protective measures to safeguard children’s health in agricultural settings. As Malaysia continues to balance agricultural productivity with public health protection, research of this nature will be essential for informing evidence-based policy decisions.

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