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Exposure to certain arsenic (As) species has been associated with increased cancer risk and a wide range of other health concerns, even at low levels. Here we used urine as a biomarker of As internal dose in a well-characterized cohort to relate diet, demographics and geography to exposure. As speciation in spot urine samples was determined for 89 participants aged ≥ 50 years from the Northern Ireland Cohort for the Longitudinal Study of Ageing (NICOLA), stratified to cover the country. Principal component analysis showed that all As species clustered together, suggesting that arsenobetaine, inorganic As (iAs) and the methylated species monomethylarsonic acid and dimethylarsinic acid forms have a common source. Seafood and alcohol consumption were positively correlated with As species, while dairy products (i.e. milk) and tap water were negatively correlated. Multiple regression analysis showed that diet explained approximately 30% of the variability in urinary iAs concentrations. Geography was not found to be a predictor of As exposure. Dairy consumption was negatively correlated and the best predictor of iAs in urine, explaining 15.9% of the variability. The majority of the variation in As biomarkers was not explained, suggesting the contribution of other sources and other non-predicted variables on As metabolism and elimination.

One of cadmium’s major exposure routes to humans is through rice consumption. The concentrations of cadmium in the global polished (white), market rice supply-chain were assessed in 2270 samples, purchased from retailers across 32 countries, encompassing 6 continents. It was found on a global basis that East Africa had the lowest cadmium with a median for both Malawi and Tanzania at 4.9 μg/kg, an order of magnitude lower than the highest country, China with a median at 69.3 μg/kg. The Americas were typically low in cadmium, but the Indian sub-continent was universally elevated. In particular certain regions of Bangladesh had high cadmium, that when combined with the high daily consumption rate of rice of that country, leads to high cadmium exposures. Concentrations of cadmium were compared to the European Standard for polished rice of 200 μg/kg and 5% of the global supply-chain exceeded this threshold. For the stricter standard of 40 μg/kg for processed infant foods, for which rice can comprise up to 100% by composition (such as rice porridges, puffed rice cereal and cakes), 25% of rice would not be suitable for making pure rice baby foods. Given that rice is also elevated in inorganic arsenic, the only region of the world where both inorganic arsenic and cadmium were low in grain was East Africa.

Arsenic in rice grain is dominated by two species: the carcinogen inorganic arsenic (the sum of arsenate and arsenite) and dimethylarsinic acid (DMA). Rice is the dominant source of inorganic arsenic into the human diet. As such, there is a need to identify sources of low-inorganic arsenic rice globally. Here we surveyed polished (white) rice across representative regions of rice production globally for arsenic speciation. In total 1180 samples were analysed from 29 distinct sampling zones, across 6 continents. For inorganic arsenic the global x~was 66 μg/kg, and for DMA this figure was 21 μg/kg. DMA was more variable, ranging from < 2 to 690 μg/kg, while inorganic arsenic ranged from < 2 to 399 μg/kg. It was found that inorganic arsenic dominated when grain sum of species was < 100 μg/kg, with DMA dominating at higher concentrations. There was considerable regional variance in grain arsenic speciation, particularly in DMA where temperate production regions had higher concentrations. Inorganic arsenic concentrations were relatively consistent across temperate, subtropical and northern hemisphere tropical regions. It was only in southern hemisphere tropical regions, in the eastern hemisphere that low-grain inorganic arsenic is found, namely East Africa (x~< 10 μg/kg) and the Southern Indonesian islands (x~< 20 μg/kg). Southern hemisphere South American rice was universally high in inorganic arsenic, the reason for which needs further exploration.

The last column in Table 1, “As air conc.” is not used in the text and was included by mistake.