Arsenic concentrations above 10μgL-1 were previously found in 89% of ground water sources in six villages of Pakistan. The present study has ascertained the health risks associated with exposure to total arsenic (tAs) and its species in most frequently consumed foods. Inorganic arsenic (iAs) concentrations were found to be 92.5±41.88μgkg-1, 79.21±76.42μgkg-1, and 116.38±51.38μgkg-1 for raw rice, cooked rice and wheat respectively. The mean tAs concentrations were 47.47±30.72μgkg-1, 71.65±74.7μgkg-1, 105±61.47μgkg-1. Wheat is therefore demonstrated to be a significant source of arsenic exposure. Dimethylarsinic acid was the main organic species detected in rice, whilst monomethylarsonic acid was only found at trace levels. Total daily intake of iAs exceeded the provisional tolerable daily intake of 2.1μgkg-1day-1 body weight in 74% of study participants due to concurrent intake from water (94%), wheat (5%) and raw rice (1%). A significant association between tAs in cooked rice and cooking water resulted in tAs intake 43% higher in cooked rice compared to raw rice. The study suggests that arsenic intake from food, particularly from wheat consumption, holds particular significance where iAs is relatively low in water. Chronic health risks were found to be significantly higher from wheat intake than rice, whilst the risk in terms of acute effects was below the USEPA's limit of 1.0. Children were at significantly higher health risk than adults due to iAs exposure from rice and/or wheat. The dietary exposure of participants to tAs was attributable to staple food intake with ground water iAs <10μgL-1, however the preliminary advisory level (200μgkg-1) was achievable with rice consumption of ≤200gday-1 and compliance with ≤10μgL-1 iAs in drinking water. Although the daily iAs intake from food was lower than total water intake, the potential health risk from exposure to arsenic and its species still exists and requires exposure control measures.

Millions of people are exposed to arsenic resulting in a range of health implications. This paper provides an up-to-date review of the different sources of arsenic (water, soil, and food), indicators of human exposure (biomarker assessment of hair, nail, urine, and blood), epidemiological and toxicological studies on carcinogenic and noncarcinogenic health outcomes, and risk assessment approaches. The review demonstrates a need for more work evaluating the risks of different arsenic species such as, arsenate, arsenite monomethylarsonic acid, monomethylarsonous acid, dimethylarsinic acid, and dimethylarsinous acid as well as a need to better integrate the different exposure sources in risk assessments.

Understanding arsenic speciation in water is important for managing the potential health risks associated with chronic arsenic exposure. Most arsenic monitoring studies to date have only measured total arsenic, with few looking at arsenic species. This study assessed 228 ground water sources in six unstudied villages in Pakistan for total, inorganic and organic arsenic species using ion chromatography inductively coupled plasma collision reaction cell mass spectrometry. The concentration levels approached 3090μgL-1 (95% CI, 130.31, 253.06) for total arsenic with a median of 57.55μgL-1, 3430μgL-1 (median=52) for arsenate (As+5) and 100μgL-1 (median=0.37) for arsenite (As+3). Exceedance of the WHO provisional guideline value for arsenic in drinking water (10μgL-1) occurred in 89% of water sources. Arsenic was present mainly as arsenate (As+5). Average daily intake of total arsenic for 398 residents living in the sampled houses was found up to 236.51μgkg-1day-1. This exposure estimate has indicated that 63% of rural residents exceeded the World Health Organization's provisional tolerable daily intake (PTDI) of 2.1μgkg-1day-1 body weight. Average daily intake of As+5 was found to be 15.63μgkg-1day-1 (95% CI, 5.53, 25.73) for children ≤16 and 15.07μgkg-1day-1 (95% CI, 10.33, 18.02) for adults. A mean daily intake of 0.09μgkg-1day-1 was determined for As+3 for children and 0.26μgkg-1day-1 for adults. Organic arsenic species such as monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and Arsenobetaine (AsB) were found to be below their method detection limits (MDLs).

Previous risk assessment studies have often utilised generic consumption or intake values when evaluating ingestion exposure pathways. If these values do not accurately reflect the country or scenario in question, the resulting risk assessment will not provide a meaningful representation of cancer risks in that particular country/scenario. This study sought to determine water and food intake parameters for one region in South Asia, rural Pakistan, and assess the role population specific intake parameters play in cancer risk assessment. A questionnaire was developed to collect data on sociodemographic features and 24-h water and food consumption patterns from a rural community. The impact of dietary differences on cancer susceptibility linked to arsenic exposure was evaluated by calculating cancer risks using the data collected in the current study against standard water and food intake levels for the USA, Europe and Asia. A probabilistic cancer risk was performed for each set of intake values of this study. Average daily total water intake based on drinking direct plain water and indirect water from food and beverages was found to be 3.5Lday-1 (95% CI: 3.38, 3.57) exceeding the US Environmental Protection Agency's default (2.5Lday-1) and World Health Organization's recommended intake value (2Lday-1). Average daily rice intake (469gday-1) was found to be lower than in India and Bangladesh whereas wheat intake (402gday-1) was higher than intake reported for USA, Europe and Asian sub-regions. Consequently, arsenic-associated cumulative cancer risks determined for daily water intake was found to be 17 chances in children of 3-6years (95% CI: 0.0014, 0.0017), 14 in children of age 6-16years (95% CI: 0.001, 0.0011) and 6 in adults of 16-67years (95% CI: 0.0006, 0.0006) in a population size of 10,000. This is higher than the risks estimated using the US Environmental Protection Agency and World Health Organization's default recommended water intake levels. Rice intake data showed early life cumulative cancer risks of 15 chances in 10,000 for children of 3-6years (95% CI: 0.0012, 0.0015), 14 in children of 6-16years (95% CI: 0.0011, 0.0014) and later life risk of 8 adults (95% CI: 0.0008, 0.0008) in a population of 10,000. This is lower than the cancer risks in countries with higher rice intake and elevated arsenic levels (Bangladesh and India). Cumulative cancer risk from arsenic exposure showed the relative risk contribution from total water to be 51%, from rice to be 44% and 5% from wheat intake. The study demonstrates the need to use population specific dietary information for risk assessment and risk management studies. Probabilistic risk assessment concluded the importance of dietary intake in estimating cancer risk, along with arsenic concentrations in water or food and age of exposed rural population.

There are limited data on exposure to mycotoxins in Pakistan. Here, we measured exposure to deoxynivalenol (DON), a common contaminant of wheat, and aflatoxin B₁ (AFB₁), a known contaminant of rice, using biomarkers of exposure. Wheat (n = 195) and rice (n = 62) samples were analyzed for AFB₁ and DON levels, and the corresponding urinary biomarkers were analyzed in urine samples from a rural population (n = 264, aged 4–80 years, male 58%) using ultra-sensitive liquid chromatography–tandem mass spectrometry. AFB₁ was detected in 66% of rice (5.04 ± 11.94 µg/kg) and 3% of wheat samples. AFM₁ (hydroxylated form of AFB₁) was detected in 69% of urine samples, mean 0.023 ± 0.048 ng/mL and DON was detected in 20% of urine samples, mean 0.170 ± 0.129 ng/mL. The maximum probable daily intake for DON derived from the urinary biomarker was 59.8 ng/kg b.w./day, which is below the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives’ tolerable daily intake (1000 ng/kg b.w./day). However, for aflatoxin, the derived margin of exposure (MoE) of (13.2) was well below the safe MoE (10,000) suggested by the European Food Safety Authority. The calculated aflatoxin-associated cancer risk of 0.514/10⁵ individuals/year suggests that measures should be taken to reduce the AFB₁ contamination in food, particularly rice, in Pakistan.