Research Roundup: Cardiovascular disease mortality, arsenic and rice in England and Wales
Research and impact 18th February 2021
PhD student and President’s Doctoral Scholar Lingqian Xu’s research has revealed an association between consumption of arsenic-bearing rice and mortality due to cardiovascular disease (CVD) in England and Wales. Lingqian’s work is adding to the increasing evidence of detrimental health outcomes arising from what have previously been widely considered to be low levels of arsenic exposure.
Inorganic arsenic has been widely recognized as a human carcinogen since at least the 1950s. A considerable number of studies have shown that inorganic arsenic exposure is associated with increased risks of detrimental impacts on various organs or body systems. Amongst these, impacts on hypertension or inflammation are amongst several plausible mechanisms contributing to increased risks of cardiovascular diseases (CVD) which are arguably the most serious non-cancer health outcomes. In fact, given the sizable global population exposed to inorganic arsenic and the high level of pre-existing CVD risks in the world, even a small inorganic arsenic-induced increase in CVD relative risks would result in a large number of additional avoidable premature deaths as well as a considerably increased burden on health services.
Much research has already connected high exposure to inorganic arsenic via drinking water with elevated CVD risks. A critical review by Lingqian revealed increasing recent evidence for this even at drinking water arsenic concentrations below the current WHO provisional guide value (also adopted as the UK and EU regulatory values) of 10 parts per billion.
Over 3 billion people in the world, including many in the UK, are further exposed to inorganic arsenic by eating rice as a staple food. Despite this, there has been to date a lack of epidemiological evidence demonstrating an association of cardiovascular disease risks with inorganic arsenic intake from rice. England and Wales seemed a useful place to explore for such an association because arsenic exposure from drinking water is comparatively low and readily quantified and because there is a wide range of rice consumption rates.
Figure 1 indicates that even from afar, the map on the right side of Lingqian’s poster clearly shows the well-known “North-South divide” in age standardised mortality rates for cardiovascular disease – the higher rates in the North indicated by red and yellow colours, relatively lower rates in South/South-East by green colours. Lingqian’s original work suggests that exposure to inorganic arsenic in rice is associated with a small (around 1 %) but significant increase in CVD mortality risks averaged across England and Wales.
Lingqian used public domain local authority level CVD mortality rates adjusted for age, gender and other well known factors otherwise known to strongly impact CVD mortality rates. These were then compared to imputed local authority level rice consumptions rates based on public domain dietary surveys and using public domain ethnicity data as a proxy for rice consumption class. Lingqian’s ecological study showed that the modelled exposure to arsenic from rice was associated with a slight (~ 1 % overall) but statistically significant elevation in local authority level CVD age-standardised mortality rates (ASMR) in England and Wales.
Lingqian’s work suggests the necessity of rice consumption management even in western countries. In particular, it is recommended that high rice consumers should consider ways in which to reduce their exposure to inorganic arsenic via this route. Given the otherwise nutritional benefits of rice consumption, eating rice in a more protective way (e.g. in selection of rice variety and type and in cooking method) might be indicated rather than not eating rice at all. Lastly, Lingqian’s work also highlights that exposure to inorganic arsenic should be considered as a potentially important confounder when otherwise exploring the key factors controlling incidence of and mortality arising from cardiovascular disease.
Adverse health outcomes, including death from cardiovascular disease (CVD), arising from chronic exposure to inorganic arsenic (iAs) are well documented. Consumption of rice is a major iAs exposure route for over 3 billion people, however, there is still a lack of epidemiological evidence demonstrating the association between iAs exposure from rice intake and CVD risks. We explored this potential association through an ecological study using data at local authority level across England and Wales. Local authority level daily per capita iAs exposure from rice (E-iAsing,rice) was estimated using ethnicity as a proxy for class of rice consumption. A series of linear and non-linear models were applied to estimate the association between E-iAsing,rice and CVD age-standardized mortality rate (ASMR), using Akaike’s Information Criterion as the principle model selection criterion. When adjusted for significant confounders, notably smoking prevalence, education level, employment rate, overweight percentage, PM2.5, female percentage and medical and care establishments, the preferred non-linear model indicated that CVD risks increased with iAs exposure from rice at exposures above 0.3 µg/person/day. Also, the best-fitted linear model indicated that CVD ASMR in the highest quartile of iAs exposure (0.375-2.71 µg/person/day) was 1.06 (1.02, 1.11; p-trend < 0.001) times higher than that in the lowest quartile (< 0.265 µg/person/day). Notwithstanding the well-known limitations of ecological studies, this study further suggests exposure to iAs, including from rice intake, as a potentially important confounder for studies of the factors controlling CVD risks.
Xu, L., Polya, D.A., Li, Q. and Mondal, D. (2020) Association of low-level inorganic arsenic exposure from rice with age-standardized mortality risk of cardiovascular disease (CVD) in England and Wales. Science of the Total Environment, 743, Art. 140534. https://doi.org/10.1016/j.scitotenv.2020.140534 (open access)
Xu, L., Mondal, D. and Polya, D.A. (2020) Positive association of Cardiovascular Disease (CVD) with Chronic Exposure to Drinking Water Arsenic at Concentrations below the WHO Provisional Guideline Value: A Systematic Review and Meta-Analysis. Int. J. Env. Res. Public Health, 17(7), Art. No. 2536. https://doi.org/10.3390/ijerph17072536 (open access)
Xu, L. and Polya, D.A. (2020) Exploratory study of the association in the United Kingdom between hypertension and inorganic arsenic (iAs) intake from rice and rice products. Environmental Geochemistry and Health. https://doi.org/10.1007/s10653-020-00573-8 (open access)