Reviewed by Lily Ramsey, LLM

A recent Scientific Reports study focussed on determining the association between arsenic exposure due to groundwater contamination and mortality rates linked to various types of malignancies, diabetes, Alzheimer's, and congenital anomalies.

Study: The association of arsenic exposure with mortality due to cancer, diabetes, Alzheimer's and congenital anomalies using Poisson regression. Image Credit: magnetix/Shutterstock.com

Background

Arsenic is one of the most toxic elements present in organic and inorganic forms. Inorganic arsenic forms commonly found in groundwater as toxic contaminants are trivalent arsenite (As III) and pentavalent arsenate (As V).

Although the main natural source of arsenic is pyrite minerals, this element is also present in many agricultural chemicals (e.g., herbicides, and insecticides), chromated copper arsenate (CCA), wood preservatives, coal burning, mining, and manufacturing industries.

More than seventy countries worldwide, including China, Nepal, India, Austria, the US, Chile, Bangladesh, Canada, and Iran, have reported the presence of arsenic in groundwater. Exposure to arsenic through groundwater contamination has been associated with many adverse health conditions.  

Upon exposure, arsenic quickly gets absorbed in the body and soon reaches the bloodstream, through which it accumulates in body tissues and causes various diseases. The International Agency for Research on Cancer (IARC) has classified arsenic as a class I human carcinogen.

The continual use of arsenic-contaminated groundwater for drinking or irrigation leads to arsenicosis or arsenic poisoning. Arsenicosis could occur in the lungs, kidney, bladder, intestine and skin.

Furthermore, arsenic poisoning causes immune-related disorders, neurological dysfunction, and cardiovascular events. Arsenic poisoning also causes stillbirth, premature birth, and abortion in pregnant women. Children exposed to a high concentration of arsenic undergo severe weight loss and malnutrition.

About the study

The present study investigated the association between the arsenic concentration in the groundwater and the mortality rates due to diabetes mellitus, malignancies, and congenital anomalies in the contaminated areas compared to other regions.

The groundwater water samples of Hamadan province were analyzed, which showed the presence of arsenic contamination in some areas, particularly Kabudarahang. More than 90% of the water in Hamadan province is used in agriculture.

All relevant data for this study were obtained from the vice-chancellor for Health of Hamadan University of Medical Sciences for a period of five years, i.e., from 2016 to 2020.

The association between arsenic level and the mortality rate per 100,000 population due to various diseases in Kabudarahang was compared with other cities of the Hamadan province using Poisson regression.

Study findings

The groundwater analysis revealed that the highest arsenic contamination of 190 µg per liter was in the rural areas of Kabudarahang, located northwest of Hamadan province.

Furthermore, some areas of Nahavand, Malayer, and Kabudahang exhibited a higher arsenic level, i.e., two to 18 times higher than the maximum residue limit (MRL). Previous studies have indicated that these regions' main source of arsenic contamination is geogenic and geological activities.

The highest mortality rate was recorded between 2016 and 2020. Poisson regressions revealed a positive and significant association between arsenic concentration and mortality due to cancers, particularly liver, breast, stomach, meningeal and brain, and leukemia.

Consistent with the findings of this study, a previous study had shown that arsenic contamination in drinking water augmented the mortality rate due to an increase in cancer diagnosis. For instance, a meta-analysis indicated a statistically significant association between long-term exposure to arsenic and liver cancer mortality.

This study established a significant association between arsenic exposure and mortality due to Alzheimer's disease. This association is supported by the fact that arsenic causes neurotoxicity and impairment of memory and cognition.

Furthermore, arsenic is also linked to many pathological processes, such as oxidative stress, apoptosis, inflammation, mitochondrial disorders, disruption of protein homeostasis, and abnormal calcium signaling. Animal studies have shown that prolonged exposure to arsenic increases insulin resistance.

Poisson Regression results indicated higher death rates due to cancer, diabetes mellitus, Alzheimer's Disease, and congenital anomalies in urban areas compared to rural regions.

These differential mortality rates could be due to higher levels of air pollution, sedentary lifestyles, overweight, depression, and hypertension in the urban population.

Conclusions

This study has two limitations. The first limitation is associated with not assessing the role of different types of arsenic separately while determining its effect on the mortality rates of a region.

The second limitation is not considering the common risk factors, such as diet, physical activity, obesity, smoking, and genetic factors, which significantly affect mortality rates.

Despite these limitations, this study presented a significant association between drinking water contaminated with arsenic and higher mortality rates due to cancers, congenital anomalies, diabetes, and Alzheimer's disease. 

Journal reference:

• Rahmani, A. et al. (2023) The association of arsenic exposure with mortality due to cancer, diabetes, Alzheimer's and congenital anomalies using Poisson regression. Scientific Reports, doi: 10.1038/s41598-023-42744-4. https://www.nature.com/articles/s41598-023-42744-4