SEGH Articles

Arsenic hazard in rice from Kandal Province, Cambodia

08 September 2014
Peter Gilbert won the student prize at SEGH 2014 for best oral presentation.

After a somewhat uneventful 14 hr flight from Manchester, England I had landed in the capital of Cambodia, had my bags ruthlessly checked in front of two armed guards, had drivers practically fighting to give me a lift to my hotel, and travelled on the back of a moped though Phnom Penh’s rush hour traffic, a journey which at the time seemed like the most dangerous ride of my life. The reason we were here; to investigate arsenic concentrations within Cambodian rice, something which at the time of research initiation, had not previously been conducted.

We were to work closely with an NGO called RDIC (Resource Development International Cambodia) who use education and community based projects to implement safe drinking water in areas of high arsenic risk. With their help this study focused on Kandal Province, a region in the south of Cambodia where tube well As concentrations exceeded 3000 µg As/L. Use of contaminated waters for irrigation of rice paddies results in rice with elevated levels of As and given that rice forms 75% of the daily calorific intake in Cambodia it is likely a major source of exposure.

So we set to the task of collecting rice samples for As analysis. Clinging to the back of my translator’s moped and laden with samples of rice we travelled between four large markets in Kandal Province, collecting rice intended for direct human consumption. The origin and variety of rice was recorded totalling 19 different varieties sourcing from 7 provinces as well as Chinese, Vietnamese and Thai imports. After navigating customs with 15 kg of rice, samples were returned to Northumbria University where total As was determined by digestion with nitric acid followed by analysis by Inductively Coupled Mass Spectrometry (ICP-MS). Cambodian grown rice was found to be elevated in As with levels comparable to other As contaminated areas such as India and Bangladesh.

To gain a better understanding of the risk this posed to the local population the second key aspect of this study consisted of a food consumption survey in the village of Preak Russey, with the aim of determining rice and water consumption rates in order to assess absolute and relative contributions to the intake of As. Located four hours south of Phnom Penh and only reachable by ferry crossing Preak Russey is an extremely poor village with agricultural based livelihoods. When As was first identified in Cambodian tube well As concentrations in Preak Russey reached up to 3000 µg As/L with 13% of the population having documented arsenicosis. Two weeks were spent in the village conducting food and water consumption surveys for 20 households through interviews with a translator. Rice was typically eaten three times a day, typically with vegetables or fish with only wealthier households affording a more varied diet containing noodles or meat.

Due to the high consumption of rice and their elevated levels of As it was found that the daily exposure to As through rice would be greater than drinking 2 L of water at the WHO recommended limit of 10 µg As/L. Equally when As ingestion is calculated from both water and rice combined the daily consumption of As breaches the limits beyond which genotoxic effects occur. This study highlights As in rice as a significant environmental hazard in Cambodia and provides a base for further research.

Peter Gilbert (p.gilbert@northumbria.ac.uk) Department of Geography, Northumbria University, England