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Dietary Arsenic Exposure in Bangladesh

Molly L. Kile
Harvard School of Public Health, Boston, Massachusetts, USA

E. Andres Houseman
Harvard School of Public Health, Boston, Massachusetts, USA

Carrie V. Breton
Harvard School of Public Health, Boston, Massachusetts, USA

Thomas Smith
Harvard School of Public Health, Boston, Massachusetts, USA

Quazi Quamruzzaman
Dhaka Community Hospital, Dhaka, Bangladesh

Mahmuder Rahman
Dhaka Community Hospital, Dhaka, Bangladesh

Golam Mahiuddin
Dhaka Community Hospital, Dhaka, Bangladesh

David C. Christiani
Harvard School of Public Health, Boston, Massachusetts, USA

Abstract/ Executive Summary:

Background: Millions of people in Bangladesh are at risk of chronic arsenic toxicity from drinking contaminated groundwater, but little is known about diet as an additional source of As exposure. METHODS: We employed a duplicate diet survey to quantify daily As intake in 47 women residing in Pabna, Bangladesh. All samples were analyzed for total As, and a subset of 35 samples were measured for inorganic arsenic (iAs) using inductively coupled plasma mass spectrometry equipped with a dynamic reaction cell. RESULTS: Median daily total As intake was 48 µg As/day [interquartile range (IQR), 33–67) from food and 4 µg As/day (IQR, 2–152) from drinking water. On average, iAs comprised 82% of the total As detected in dietary samples. After adjusting for the estimated inorganic fraction, 34% [95% confidence interval (CI), 21–49%] of all participants exceeded the World Health Organization’s provisional tolerable daily intake (PTDI) of 2.1 µg As/kg-day. Two of the 33 women who used a well with < 50 µg As/L exceeded this recommendation. CONCLUSIONS: When drinking water concentrations exceeded the Bangladesh drinking water standard of 50 µg As/L, ingested water was the dominant source of exposure. However, as drinking water As concentrations decrease, the relative contribution of dietary As sources becomes more important to ingested dose. The combined intake from both diet and drinking water can cause some individuals to exceed the PTDI in spite of using a tube well that contains < 50 µg As/L.

Keywords: Arsenic, Bangladesh, Dose, Duplicate diet, Food, Intake, Water

Location: In Bangladesh

Start Date: 00-00-2004

End Date: 00-00-2004

Program Area: Risk Management in Agriculture

Commodity: Soil Arsenic, Water Arsenic

Objectives:

To determine the Dietary Arsenic Exposure in Bangladesh

Methodology:

Participant selection: Forty-seven women who had previously taken part in a longitudinal study investigating As exposure and biomarker response, and who identified themselves as the primary food preparer in the family were invited to participate in this study (Kile et al. 2005). All women agreed to participate, and informed consent was obtained. Two sampling periods were scheduled for 3 consecutive days in winter (January–March 2004) and for 3 consecutive days in summer (June–August 2004). Participants received compensation (US$9) after each sampling period. The institutional review boards at Harvard School of Public Health and Dhaka Community Hospital approved the protocol for this study. Food samples: Participants were instructed to save duplicate portions from each meal in separate polypropylene resealable bags. Researchers visited each participant after the midday and evening meals to collect samples, which were kept refrigerated until processing. Each evening, individual portions were weighed in order to determine dietary intake rates. The portions from each participant were then homogenized into a 24-hr composite sample (n = 282) using a blender. Homogenized samples were aliquotted into polyethylene tubes and frozen at –4°C and shipped on dry ice. Field blanks, composed of 50 mL Milli-Q 18.2 Ω analytical grade water (Millipore Corporation, Billerica, MA, USA), were collected after every eighth sample. For the field blanks, the water underwent the same homogenization process as the food samples and was preserved with reagent grade nitric acid (Merck, Darmstadt, Germany) to a pH of < 2. Composite samples were subjected to microwave acid digestion with nitric acid and analyzed for total As using dynamic reaction cell inductively coupled plasma-mass spectrometry (ICP-DRC-MS) with oxygen as the cell gas (Model 6100 DRC; PerkinElmer, Norwalk, CT, USA). This analytical method detects As oxide species (⁷⁵As¹⁶O⁺) at mass 91 and avoids argon chloride interference (Bollinger and Schleisman1999). Drinking water: All women reported having their own tube well and using it for all water for drinking and cooking purposes. Participants were provided with two 4-L polyethylene containers and instructed to place an identical quantity of water in the containers immediately after drinking a glass of water in order to determine drinking water intake rates. However, the concentration of As in each participant’s tube well was estimated using water samples collected as part of a larger, longitudinal biomarker study in which water samples were collected for 3 consecutive days every 3 months (Kile et al. 2005). Data from 2004, representing 12 samples per participant and overlapping the time frame of this duplicate diet study, were used to establish an average annual drinking water As concentration for each participant. Total As was measured by Environmental Laboratory Services (North Syracuse, NY, USA) using ICP-MS following U.S. EPA method 200.8 (U.S. EPA 1994). Statistical analysis: We recorded the weight of each duplicate meal portion (grams wet weight) and the volume of drinking water (milliliters) collected in a 24-hr period as the daily dietary intake rate and drinking water intake rate, respectively. Descriptive statistics were calculated, including mean ± SD. We calculated daily total As intake from food (micrograms per day) for each participant using the total wet weight of food consumed each day multiplied by the total As concentration measured in the corresponding 24-hr composite sample (micrograms per gram wet weight).

Source of Information: Environmental Health Perspectives, VOLUME-115, NUMBER-6, June 2007

Article Link (Online Journal):

Funding Source:

1.

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The median drinking water concentration for the 47 tube wells sampled was 1.6 μg/L (range, < 1–450 μg/L). Overall, 60% were below the WHO’s 10-μg/L drinking water standard (WHO 1985), and 70% were below the Bangladesh drinking water standard of 50 μg/L (BGS and DPHE 2001). On average, participants consumed 1,636 g food (wet weight) and 2,676 mL water per day. Participants consumed significantly more food in winter (1,700 ± 338 g wet weight) than in summer (1,571 ± 324 g wet weight), but no seasonal difference was detected in the concentration of As in the composite food samples. The number of servings collected did not vary significantly over the course of the study. Also, we did not find a significant difference in the amount of food collected within each season. No seasonal or daily difference was observed in the drinking water intake rate. The frequency of each food type collected in the duplicate diet study is shown in Table 2. Vegetables and rice were the most commonly consumed food items. Rice, the dietary staple, was present in 91% of all collected meals, with 405 g (wet weight) consumed in an average serving. Vegetables were present in 94% of all meals collected, with an average serving size of 72 g wet weight. Freshwater fish was the most commonly consumed protein. Pabna is far enough inland that seafood is not readily available in the local markets, and no participants reported eating either seafood or shrimp during this study period. Furthermore, all participants reported purchasing their food at local markets. These items would most likely be produced domestically, if not locally. However, this data was not collected.

Knowledge Management: Journal