A multidisciplinary investigation into arsenic contamination in rice : rice preparation, arsenic knowledge and risk perception

Mwale, T

Abstract

Rice is a popular staple consumed by approximately 3 billion of the world’s population. It is a source of essential nutrients, carbohydrates, protein, vitamins and fibre. However, despite its
high nutritional content, rice is the second most important route after water, for human exposure to arsenic (As) through the diet. Hence, awareness of As contamination in rice and use of mitigation techniques to reduce the As content of rice are vital.

The Overall aim of this thesis was to determine the As contamination levels in cooked rice considering different cooking methods used across the world and any effect of such cooking
techniques on essential elements present in rice. Since consumption of rice and rice-based products are on the rise in the UK, one of our goals were to determine the awareness and risk
perception of As exposure from rice intake in a UK population using a questionnaire based survey. Apart from rice, presence of As in other grains were also summarised using a systematic literature review.

The effect of cooking techniques on both As and essential elements showed a decrease in As of 4.5%, 30%, and 44% after using rice-to-water ratios of 1:3, 1:6 (p = 0.004), and 1:10 (parboiling; p < 0.0001) respectively. Similarly, increase in cooking water caused a decrease in essential elements, with the most decrease observed in potassium (K) (50%) and the least in copper (Cu) (0.2%) in comparison to the other elements. A further laboratory-based study
investigated the As content of Sri Lankan rice and its association with CKDu. Results obtained were compared to existing literature and although it was established that rice from CKDu endemic areas might contain As, further investigation on the ecological risk of CKDu from As in rice is required. Results from the questionnaire survey revealed that general knowledge of As amongst the White British and ethnic minority groups was high. However, very few
participants were aware of As contamination in rice. Prior knowledge of As in rice did not always result in the use of recommended practices. In comparison to consumers from the
ethnic minority groups, the White British were more favourably inclined to reduce the amount and frequency of rice consumed, and consider food options other than rice. Thus, suggesting that the other ethnicities have low to no risk perception of As exposure through rice consumption whilst the White British may perceive risk of exposure to As from rice. Furthermore, results obtained from the survey revealed that apart from rice, other popular grains consumed include wheat, maize/corn and oats. This information formed the basis of the systematic literature review in chapter 7 and the results obtained showed that As contamination was higher (above 0.5 mg/kg limit for China and 1 mg/kg for Australia and New
Zealand) in maize and millet in comparison to the other cereal grains. Results from this research could help rice eating communities to choose the best practice for rice preparation
and consumption. Additionally, survey data provide unique information on dietary habits of ethnic minority groups, essential for dietitians and health professionals.

• Thesis Type: Thesis
• Acceptance Date: Apr 30, 2019
• Deposit Date: May 7, 2019
• Publicly Available Date: Jun 7, 2019