Can drinking water contamination harm our head?

In recent years, awareness of the role played by water pollution in the development of neurodegenerative diseases has increased significantly [1]. Neurotoxicity is an etiological phenomenon involving alteration of the structure and function of the central nervous system mediated by a biological, chemical or physical agent [2]. It contributes to disorders such as Alzheimer’s and Parkinson’s diseases, cognitive disorders, neurovascular diseases (e.g., brain aneurysms), neurodevelopmental diseases such as attention deficit hyperactivity disorder (ADHD) and autism spectrum disorders (ASD).

Currently, neurodegenerative diseases are one of the leading causes of mortality and disability worldwide, and researchers predict that their numbers will increase in the future [1]. Unfortunately, one significant source of hazardous substances can be drinking water.

Drinking water contamination – main factors

Of all the pollutants, the effects of heavy metals such as selenium, cadmium, arsenic, nickel, mercury, chromium, lead, zinc and cobalt have been best described [3]. However, in the context of water quality, we also see the significant presence of pesticides and fertilizers [4], disinfection by-products [5] and persistent organic pollutants [5]. Some of them may exhibit neurotoxic effects.

In accordance with the Decree of the Minister of Health dated December 7, 2017. on the quality of water intended for human consumption, it should meet a number of requirements for microbiological and chemical parameter values [6]. Among the ions and compounds included in the Ordinance are those with confirmed or suspected neurotoxic effects. The list will certainly be updated with more substances. What limits us in adopting more stringent quality standards is awareness of environmental risks. Although today we consider the concentrations included in the Ordinance to be safe, we cannot exclude the possibility that in the future these values will be lowered and adapted to growing scientific knowledge.

Although the risk of sudden contamination of drinking water with dangerous neurotoxins seems abstract in our conditions, the experience of, for example, the water crisis in the city of Flint (USA) [7] shows that local statutory negligence can lead to a huge threat to human life and health, imprinting the stigma of environmental inequality on future generations [8].

The effects of neurotoxic agents depend on the time of exposure, the dose and the sensitivity of the body. It is estimated that about 70,000. chemicals cause neurotoxicity, but the mechanism and effects have been described for only 10 percent. of them [1].

The role of disinfection by-products in drinking water

The process of disinfecting drinking water is essential to ensure microbiological safety, especially if it has to travel many miles of water mains before reaching consumers. However, the chemicals used in the disinfection process (e.g., chlorine dioxide, sodium hypochlorite, chlorine gas, ozone), reacting with residual organic matter in the water and biofilms present in the installations, can produce so-called “biofilms”. disinfection by-products. This is a numerous (more than 600 substances confirmed in drinking and pool water) and diverse group of substances (from chloramines and chloroform to halogenoacetic acids and halogenoacetonitriles) [9].

Most disinfection by-products have neurotoxic properties and activate oxidative stress response pathways [10]. However, strong evidence of the effect of tap water consumption on the development of neurodegenerative and neurodevelopmental diseases is scarce. Studies show that pregnant women who consume water with elevated concentrations of trihalomethanes, chloramines and other compounds from the disinfection by-product group have an increased risk of the baby developing neurodevelopmental defects [11].

The more natural organic matter there is in the water, the more undesirable compounds will be formed, which will worsen the quality of the water, but will also have a negative impact on our health. It is projected that as a result of climate change, the annual increase in the concentration of disinfection by-products in drinking water in the Northern Hemisphere could range from 2.7 to as much as 9.5 percent. [12]. In developed countries, technology is available to achieve a high degree of organic matter removal, but this is associated with an increase in the cost of drinking water treatment.

Climate change shapes the quality of water resources

Increasingly, climate change is cited among the potential drivers of water pollution due to its strong impact on the quality of drinking water supplies [13]. Climate change affects entire biological systems. In addition to rising temperatures, which have degenerative effects on neurons, the increase in the potential for the formation of certain groups of pollutants and their migration in ecosystems poses a serious threat to water resources [13].

For example, water temperature and rainfall intensity affect the amount of natural organic matter (compounds derived directly or indirectly from the cells and tissues of living organisms, plant and animal) in surface and groundwater [14]. As microorganisms intensify their activities at higher temperatures, the products of their metabolism also increase, which in turn translates into the formation of so-called “microorganisms”. By-products of disinfection in drinking water.

Algal blooms and neurodegeneration in humans

As temperatures rise, so does the risk of algae and cyanobacteria blooms in surface waters [15]. In Europe, both surface water and groundwater are sources of drinking water resources. However, as much as 75 percent comes from rivers and surface reservoirs, according to WISE – Freshwater [16].

The increase in the frequency and scale of algae and cyanobacteria blooms in rivers and reservoirs means that the amount of natural organic matter in the water is increasing, but so is the risk of the toxins they produce [17]. Some of them can survive wastewater treatment processes and find their way into water for consumption [13]. Studies show that some types of cyanotoxins are able to survive in the digestive tract. This carries the risk of neurodegeneration by affecting the microbiome-gut-brain axis [18].

Aluminum and iron salts (known as coagulants) are commonly used in aiding the treatment of surface water. Coagulants eliminate turbidity by precipitating a flocculent suspension [19]. A change in pH due to an algal bloom can negatively affect the coagulation process and cause an increase in metal ions in the treated water. One analysis showed that concentrations of dissolved aluminum in water with a near-neutral pH range from 1 to 50 micrograms/liter. On the other hand, a decrease in the pH and an increase in the amount of organic matter cause an increase in the concentration of aluminum to 500-1000 micrograms/liter [14].

Assessing the real scale of the risk of neurodegenerative diseases resulting from the consumption of contaminated water is very difficult, because the development of these diseases is influenced by many factors, including environmental pollution from other sources. The last decade has brought an intensive development of knowledge about the importance of water pollution in the pathogenesis of non-communicable diseases, including neurodegenerative diseases. Both more effective protection of water resources and continuous adjustment of quality standards are needed. We must remember that one of the key factors that already determines the quality of water resources is climate change.

Dr.-Ing. Edyta Łaskawiec – water and wastewater technologist, scientist at the Zabrze Institute of Fuel and Energy Technology, science popularizer, author of an educational profile on Instagram platform: wastewater_based.doctor.

In the article, I used, among others. From the works:

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