Pesticide Residues in a Protected Tropical Water Catchment: Baseline Evidence and Implications for Long-Term Drinking Water Safety in Malaysia

Lim, Siong Hee and Sam Froze, Jiee and Anselm Su, Ting and Helmy, Hazmi and Neilson Richard, Seling and Romano, Ngui and Timothy Adrian, Jinam and Dayang Suhana, Abang Madzhi (2026) Pesticide Residues in a Protected Tropical Water Catchment: Baseline Evidence and Implications for Long-Term Drinking Water Safety in Malaysia. INTERNATIONAL JOURNAL OF RESEARCH AND INNOVATION IN SOCIAL SCIENCE (IJRISS), 10 (4). pp. 4438-4446. ISSN 2454-6186

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Abstract

This study investigated pesticide residues in raw water from the Sarawak Kiri River catchment, a critical drinking water source supplying the Batu Kitang Water Treatment Plant in Sarawak, Malaysia. Despite the presence of surrounding agricultural activities, comprehensive multi-residue analysis covering acid herbicides, organochlorine, organophosphate pesticides, and other herbicides revealed concentrations below method detection limits in samples collected in January 2025. While these findings suggest an absence of detectable contamination at the point of abstraction, interpretation requires caution. Non-detection does not necessarily equate to absence of risk, particularly given temporal variability, episodic runoff events, and limitations inherent in analytical detection thresholds. The apparent absence of pesticide residues may reflect a combination of low-intensity agricultural practices, effective riparian buffering, hydrological dilution due to high rainfall, and regulatory protection of the catchment. Importantly, the findings highlight a critical window of opportunity for proactive protection of a relatively uncontaminated water source in a region undergoing gradual land-use transition. This study underscores the need for longitudinal monitoring, event-based sampling, and integration of emerging contaminants into surveillance frameworks to ensure long-term drinking water safety. The results contribute to evidence-based water resource management in tropical catchments and provide a baseline for future environmental risk assessments.

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