Assessing Rainwater Quality Across Regions in Thailand: Implications for Public Health and Water Management

Abstract

           Background: Recognizing the impact of contaminated water on public health, ensuring access to high-quality water is critical for improving health outcomes. Rainwater, a significant natural resource in Thailand, exhibits varying compositions across regions, directly influencing overall water quality and consequently affecting public health. Therefore, there is a need to conduct comprehensive surveys to assess rainwater suitability for household use.

           Purpose: This study aimed to survey the quality of rainwater in Thailand by determining the composition as physical, chemical and biological in accordance with the Department of Health Guidelines for Drinking Water Quality (2020) of Thailand.

           Methods: From November 2022 to February 2024, 152 rainwater samples were collected from six regions: north, northeast, central, east, southern east coast, and southern west coast of Thailand. The water analysis followed the Standard Methods for the Examination of Water and Wastewater (23rd edition). Descriptive statistics were applied to analyze data across 82 parameters, including 21 criteria aligned with the Guidelines for Drinking Water Quality and 61 parameters focusing on pesticide substances.

           Results: A comprehensive analysis of the 152 rainwater samples revealed that every sample exhibited at least one parameter failing to meet water quality standards. Key concerns included acidic pH levels observed in 80% of samples and excessive coloration exceeding permissible limits in 20% of samples. Bacterial contamination, predominantly total coliform bacteria, was widespread, detected in approximately 87% of samples, surpassing occurrences of Escherichia coli. Mercury contamination was identified in a single sample from northeast Thailand, highlighting localized chemical risks. Pesticides, such as carbamates, organophosphates, pyrethroids, and glyphosate, were sporadically detected in the southern region. These findings underscore the urgent need to enhance and enforce water quality standards before promoting widespread consumption of rainwater.

          Conclusions: A comprehensive analysis of the 152 rainwater samples revealed that every sample exhibited at least one parameter failing to meet water quality standards. Key concerns included acidic pH levels observed in 80% of samples and excessive coloration exceeding permissible limits in 20% of samples. Bacterial contamination, predominantly total coliform bacteria, was widespread.