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

Keep up to date

Submit Content

Members can keep in touch with their colleagues through short news and events articles of interest to the SEGH community.

Science in the News

Latest on-line papers from the SEGH journal: Environmental Geochemistry and Health

  • Date palm waste biochars alter a soil respiration, microbial biomass carbon, and heavy metal mobility in contaminated mined soil 2017-04-19

    Abstract

    A 30-day incubation experiment was conducted using a heavy metal-contaminated mined soil amended with date palm feedstock (FS) and its derivative biochars (BCs) at three pyrolysis temperatures of 300 (BC-300), 500 (BC-500), and 700 °C (BC-700) with different application rates (0.0, 5, 15, and 30 g kg−1) to investigate their short-term effects on soil respiration (CO2–C efflux), microbial biomass carbon (MBC), soil organic carbon (SOC), mobile fraction of heavy metals (Cd, Cu, Pb, Zn, Mn, and Fe), pH, and electrical conductivity (EC). The results showed that FS and BC-300 with increasing addition rate significantly reduced soil pH, whereas SOC, CO2–C efflux, and soil MBC were increased compared to the control. On the contrary, BC-500 and BC-700 increased soil pH at early stage of incubation and have small or no effects on SOC, CO2–C efflux, and MBC. Based on the results, the date palm biochars exhibited much lower cumulative CO2–C efflux than feedstock, even with low-temperature biochar, indicating that BCs have C sequestration potential. Applying BC-700 at 15 and 30 g kg−1 significantly reduced cumulative CO2–C efflux by 21.8 and 45.4% compared to the control, respectively. The incorporation of FS into contaminated soil significantly increased the mobile content of Cd and Mn, but decreased the mobile content of Cu. However, BC-300 significantly reduced the mobile content of Cd, Cu, Pb, and Zn. It could be concluded that low-temperature biochar could be used as a soil amendment for reducing heavy metal mobility in mining contaminated soil in addition to minimize soil CO2–C efflux.

  • Historical record of anthropogenic polycyclic aromatic hydrocarbons in a lake sediment from the southern Tibetan Plateau 2017-04-17

    Abstract

    High-altitude lake sediments can be used as natural archives to reconstruct the history of pollutants. In this work, the temporal distribution of polycyclic aromatic hydrocarbons (PAHs) was determined in a sediment core collected from the southern Tibetan Plateau (TP), which was dated by using the 210Pb dating method and validated with the 137Cs fallout peak. The concentrations of the anthropogenic PAHs (Σ8PAH) in the sediment core ranged from 0.83 to 12 ng/g dw, and the fluxes of the Σ8PAH were in the range of 2.1–27 g/cm2/year. The temporal variations in the concentration and input flux of anthropogenic PAHs were low with little variability before the 1950s, and then gradually increased from the 1950s to the 1980s, and an accelerated increase was observed after the early 1980s. The content of total organic carbon played an insignificant role in affecting the time trends of PAHs in the sediment core. Diagnostic concentration fractions of PAH components indicate PAHs in the lake sediment of the southern TP which are mainly from biomass burning and/or from long-range atmospheric transport.

  • Determination of the potential implementation impact of 2016 ministry of environmental protection generic assessment criteria for potentially contaminated sites in China 2017-04-12

    Abstract

    The Ministry of Environmental Protection of China issued a 3rd draft edition of risk-based Generic Assessment Criteria (the MEP-GAC) in March 2016. Since these will be the first authoritative GAC in China, their implementation is likely to have a significant impact on China’s growing contaminated land management sector. This study aims to determine the potential implementation impact of the MEP-GAC through an in-depth analysis of the management context, land use scenarios, health criteria values adopted and exposure pathways considered. The MEP-GAC have been proposed for two broad categories of land use scenarios for contaminated land risk assessment, and these two categories of land use scenarios need to be further delved, and a MEP-GAC for Chinese cultivated land scenario ought to be developed, to ensure human health protection of Chinese farmers. The MEP-GAC have adopted 10−6 as the acceptable lifetime cancer risk, given the widespread extent and severe level of land contamination in China, consideration should be given to the decision on excess lifetime cancer risk of 10−5. During risk assessment process in practice, it is better to review the 20% TDI against local circumstances to determine their suitability before adopting it. The MEP-GAC are based on a SOM value of 1%, for regions with particularly high SOM, it might be necessary to develop regional GAC, due to SOM’s significant impact on the GAC developed. An authoritative risk assessment model developed based on HJ25.3-2014 would help facilitate the DQRA process in practice. The MEP-GAC could better reflect the likely exposures of China’s citizens due to vapour inhalation by using characteristics of Chinese exposure scenarios, including China-generic building stock, as inputs into the Johnson and Ettinger model as opposed to adoption of the US EPA parameters. The MEP-GAC once implemented will set the trajectory for the development of the investigation, assessment and remediation of land contamination for years.