Based on a recent risk assessment conducted by the European Food Safety Authority (EFSA), European consumers’ dietary exposure to inorganic arsenic is a health concern. The findings of the latest risk assessment reaffirm the outcome of EFSA’s previous risk assessment of inorganic arsenic in foods, which was conducted in 2009.

Also in response to a request by the European Commission, EFSA is currently assessing the potential risks linked with exposure to organic arsenic in food. Once this risk assessment is completed, the possible risks of combined exposure to organic and inorganic arsenic in food will be assessed. These assessments will be finalized by early 2025.

Inorganic arsenic is a widely-occurring toxic heavy metal that is especially present in rice and rice-based products, and grains and grain-based products. Drinking water can also be a significant source of exposure to the chemical. The European Commission asked EFSA’s Panel on Contaminants in the Food Chain (CONTAM Panel) to update its assessment of inorganic arsenic to consider new studies on its toxic effects.

Taking into account only human epidemiological data in its assessment, EFSA associated long-term consumption of inorganic arsenic with a range of adverse effects on human health, including cancer of the skin, bladder, and lungs; low birth weight, miscarriage, stillbirth, and infant mortality; congenital heart disease; ischemic heart disease; neurodevelopmental effects; respiratory disease; chronic kidney disease; atherosclerosis (thickening or hardening of the arteries); and skin lesions.

EFSA concluded the increased incidence of skin cancers associated with inorganic arsenic exposure to be the most critical harmful effect, and established a reference point of 0.06 micrograms per kilogram of bodyweight (µg/kg BW) per day, which represents the lowest dose of inorganic arsenic that could be associated with increased induction of skin cancer. This reference point, which is lower than the range of reference points established by the CONTAM Panel in 2009 (0.3–8 µg/kg BW per day), is also protective against the other adverse health effects in humans.

When assessing genotoxic and carcinogenic substances that are unintentionally present in the food chain, EFSA calculates a margin of exposure (MOE) for consumers. The MOE is a ratio of two factors—the dose at which a small but measurable adverse effect is observed, and the level of exposure to a substance for a given population. A low MOE represents a greater risk than a high MOE.

Based on the available data from human studies, an MOE of 1 or less would correspond to an exposure level to inorganic arsenic that might be associated with an increased risk of skin cancer. Based on the recent risk assessment, in adults, MOEs range between 2 and 0.4 for average consumers, and between 0.9 and 0.2 for high consumers. Even considering the uncertainties of the risk assessment, this finding indicates a health concern for the European population. The CONTAM Panel experts are 69 percent certain that high consumers of inorganic arsenic (at the 95th percentile) may have an increased risk of developing skin cancer.

Certain limitations and uncertainties were identified in the risk assessment. For example, in some studies, exposure was estimated based on the levels of inorganic arsenic measured in urine, which reflects exposure from both drinking water and food. However, other studies reported the concentration of inorganic arsenic in drinking water. In these cases, the reported concentrations were transformed into exposure estimates using the average body weight of those exposed, their estimated daily water intake, and additional exposure from food. There is also uncertainty regarding the variability in susceptibility to inorganic arsenic toxicity due to genetic differences between individuals. As the hazard characterisation is based on the results of large epidemiological studies, individuals who are more susceptible to adverse health effects associated with inorganic arsenic exposure due to their genetics may not be sufficiently represented in these studies.

The updated risk assessment also identifies data gaps and recommends future work to better understand certain aspects of arsenic’s health effects, such as the underlying molecular mechanism of arsenic that causes DNA damage, the role that human variations play in the susceptibility to arsenic-related health conditions, how arsenic can lead to epigenetic alterations and the associated disease risk in exposed populations, the interplay between epigenetic and genetic alterations induced by inorganic arsenic, and health effects of pre- and perinatal exposure to arsenic and how arsenic-induced alterations occurring during early life can impact the risk of disease in adult life. In addition, EFSA recommends the development of further guidance on the use of human data in risk assessments.