Table of Contents
Background
Aluminum (Al) is the most abundant metal in the earth’s crust and exists in the environment in various forms. The element is non-toxic to humans at small concentrations but its higher exposure levels can cause health issues. Overall, Al is an essential element for life but exposure to its high levels should be limited for maintaining human health. Al can be present in drinking water because of natural sources or human activities. Naturally, Al can leach down from soil and rocks into groundwater whereas, human activities comprise industrial or agricultural activities, mining, refining, and manufacturing processes. Al compounds are often used as coagulants in water treatment plants to remove particles and impurities from water. If not properly treated, excess Al can end up in the drinking water.
Various consumer products such as Al cans, foils, and cookware can contain Al. Although the release of Al from these items into the environment is minimal, these can be a source of Al discharge. Moreover, land development activities including construction, mining, and landfills can also contribute to Al release in the environment and contaminate the nearby water sources. From mentioned anthropogenic sources, Al can become part of discharge and contaminate water reservoirs through runoff and leaching processes. It is important to mention that even though, the detected Al levels in drinking water are usually low and not considered a major health concern. However, controlling and monitoring the levels of Al in drinking water is very important to prevent high levels of exposure to Al and avoid any possible health risks.
In the US, Al levels in drinking water are regulated by EPA which has set the SMCL of 0.05-0.2 mg/L in drinking water. The SMCLs are non-enforceable standards that are based on the taste, odor, and color of the water. According to the EPA, drinking water at most places meets the SMCL for Al and contains very low Al levels in drinking water. However, some communities consuming water with slightly acidic pH or those who use surface water sources may have higher Al levels in their drinking water. It is recommended that people with kidney issues, infants, and elderly people should be careful in consuming Al-contaminated drinking water. Water utilities in the US are responsible for monitoring and reporting Al levels in their drinking water to the EPA. If you are concerned about the Al levels in your drinking water, you can contact your local water utility for further information related to Al in your water supply. As mentioned, chronic exposure to high Al levels may trigger health issues in humans mainly including neurological impacts such as memory loss or confusion, and kidney problems which may also increase the risk of developing bone diseases.
Some studies also support the evidence of an association between long-term Al exposure and Alzheimer’s disease. It is believed that infants and children are more susceptible to Al toxicity compared to adults because of the development stage which makes them vulnerable to toxic exposure as the enzymatic machinery to catalyze the detoxification processes are poorly developed causing accumulation of Al in the body tissues. Further, high Al exposure to infants and children may also affect their growth and cause developmental problems. Respiratory problems such as lung irritation and fibrosis can also be caused due to Al toxicity. Therefore, Aluminum levels in drinking water should be tested and monitored on regular basis, and in case, high Al concentrations are detected in drinking water, it should be subjected to a suitable water treatment process in order to keep its level below the MCL and ensure safe drinking water supply to the consumers.
There is some epidemiological evidence that supports a link between elevated levels of Al in drinking water and health effects. Studies have found that people who live in areas with high levels of aluminum in their drinking water have an increased risk of developing Alzheimer’s disease and other neurological disorders (Van Dyke et al. 2021). Additionally, animal studies have found positive correlations between high Al exposure and brain damage along with other neurotoxic effects (Prakash and Kumar 2013). These animal studies provide further evidence that high levels of aluminum in drinking water may be harmful. It should be noted that more research is needed to fully understand the mechanisms associated with the potential health effects of Al in drinking water since the epidemiological data is limited or absent in major regions where the Al levels can be potentially high in drinking water.
Al toxicity may results from the accumulation of Al in various body tissues and organs, leading to cellular and molecular changes that can result in adverse health effects. The exact mechanisms underlying Al toxicity are not fully understood so far, but several theories have been proposed. One suggests that Al interferes with the enzyme functions and other proteins by binding to the hydroxyl groups on their surface. This binding can cause changes in the structure and function of enzymes and other proteins, leading to cellular dysfunction (Haug and Foy 1984; Jaishankar et al. 2014). Others suggest that Al interferes with the function of the blood-brain barrier, allowing aluminum to cross into the brain and cause damage to neurons (A Yokel 2012; Yokel 2006).
Studies have shown that aluminum can accumulate in the brains of animals exposed to high levels of Al, leading to neuronal degeneration and other brain damage. Further, it has also been suggested that Al disrupts the ionic balance in the cell which is essential to the human body such as Ca and P resulting in bone disorders and other health issues (Exley and Birchall 1992; Mizuno et al. 2022). Among occupationally exposed workers, Al has been proven to generate free radicals causing oxidative stress and DNA damage (Samir and Rashed 2018). However, no epidemiological data exist to date explaining Al toxicity associated with oxidative stress in the population exposed to Al through drinking water. This suggests a need for further research to reveal the mechanism of toxicity among exposed human subjects using Al contaminated drinking water by comparing water and biological data.
Detection Methods and Removal Strategies
Al can be detected/monitored in drinking water using various described methods. Standard methods recommend the AAS-based methods i.e. FAAS or GFAAS for Al quantification in drinking water. This method is cost-effective with high sensitivity and low detection limits up to ppm level with high precision. However, if high sensitivity is desired, ICP is considered the most effective method when coupled with mass spectrometer MS or OES to give results upto µg and ng levels. Furthermore, ICP is also preferred where Al concentrations need to be measured for human biological samples such as blood, urine, etc. since these matrices contain very low amounts of Al.
However, the limitation of using ICP includes expensive costs to quantify metals and should only be recommended when the desired results are at very low concentrations. Ion chromatography is also a very effective method for the quantification of ionic species of Al. The method separates Al ions from other ions in water by passing a sample through a column filled with a resin bed that binds and separate Al ions from water. Other commonly used methods for Al detection include colorimetry in which colored complexes of Al are formed when a reagent is added to a water sample. However, colorimetric methods are used where only estimated measurements of Aluminum in water are desired.
Several methods have been proposed for efficient Al removal from drinking water. Among widely used methods include reverse osmosis which uses a semipermeable membrane to pass through water with pressure resulting in the removal of Al in drinking water (Wenten 2016). At a small scale, distillation is also very effective in removing Al by heating water to generate steam followed by cooling that results in the removal of Al from water. The ion exchange method using a resin bed of ions that results in the exchange of ions in water also removes Al from the drinking water effectively (Petrie et al. 1984).
Electrocoagulation is also used for removing Al from water which uses electric current to coagulate particles in water including Al ions and separate them from the water (Ray et al. 2004). Activated alumina has also been proven very effective for removing Al from drinking water by removing Al ions through their adsorption on the surface medium. Moreover, the coagulation-flocculation method using chemicals such as Al-sulfate (alum) to coagulate Al particles in water, forming flocs is also a very cost-effective and routinely used method for Al removal from drinking water.
Public Perspective
Following frequently asked questions (FAQs) try to address some general public concerns in the US, especially the NYC region.
The EPA has set a Secondary Maximum Contaminant Level (SMCL) of 0.05–0.2 milligrams per liter (mg/L) for Al in drinking water. This level is set to protect from changing the color of the water.
Exposure to Al is usually not harmful, but exposure to high levels for long periods can affect your health. Toxicity occurs at concentrations of more than 100 µg/L. Also, urine Al concentrations below 55 μg/g of creatinine are considered safe for humans.
Reverse osmosis (RO) is considered the most effective option for reducing Al from drinking water, with the capacity of removing about 98% of all its content. Water distillation is also highly efficient in the water treatment process, with these systems able to remove more than 99% of Al from drinking water.
Acute Al toxicity (500 μg/L or more) may affect even normal kidney function leading to the symptoms like grand mal epilepsy, coma, or death within weeks.
Though not discussed often, Al is one of the significant sources of water pollution primarily due to its abundant natural occurrence and industrial use. Al is a versatile material due to its excellent properties such as lightweight, corrosion resistance, long life, and electrical conductivity.
Boiling water kills pathogens only. No amount of boiling can remove heavy metals, fuel, or chemicals from contaminated water. In dealing with water contaminated with heavy metals and other chemicals, distillation can be an effective method of removing these contaminants from water.
RO filtration achieves a very high level of heavy metal removal by means of an RO membrane. These filters can remove 97-98% of Al from drinking water. A professional water testing services is recommended to see the efficiency of the filter
Al can accumulate in the kidneys, brain, lungs, liver, and thyroid where it competes with calcium for absorption and can affect skeletal mineralization. In infants, Al can slow growth. Al also attacks your central nervous system.
No known physiologic need exists for Al. However, because of its atomic size and electric charge (0.051 nm and 3+, respectively), Al is sometimes a competitive inhibitor of several essential elements with similar characteristics, such as Mg (0.066 nm, 2+), Ca (0.099 nm, 2+), and Fe (0.064 nm, 3+).
If you have any of the following symptoms, see your doctor, especially if you have kidney disease or are on dialysis: Confusion. Muscle weakness. Bone pain, deformities, and fractures.
No evidence exists on Al leads to cancer, especially through drinking water exposure.
Conclusion
Overall, the drinking water in the US is safe to drink with very low concentrations of Al reported so far. The metal can be toxic to human health and cause various health problems when consumed in high concentrations and for long periods. USEPA has regulated the levels of Al in drinking water by setting an SMCL based on its aesthetic effects related to odor, smell, and taste. Regular monitoring and testing drinking water for aluminum should be conducted by authorities to ensure a safe drinking water supply to US consumers for public health safety.
References
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Haug A, Foy CE. 1984. Molecular aspects of aluminum toxicity. Critical Reviews in Plant Sciences. 1(4):345-373.
Jaishankar M, Tseten T, Anbalagan N, Mathew BB, Beeregowda KN. 2014. Toxicity, mechanism and health effects of some heavy metals. Interdisciplinary toxicology. 7(2):60.
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Petrie JJ, Fleming R, McKinnon P, Winney RJ, Cowie J. 1984. The use of ion exchange to remove aluminum from water used in hemodialysis. American Journal of Kidney Diseases. 4(1):69-74.
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Van Dyke N, Yenugadhati N, Birkett NJ, Lindsay J, Turner MC, Willhite CC, Krewski D. 2021. Association between aluminum in drinking water and incident alzheimer’s disease in the canadian study of health and aging cohort. Neurotoxicology. 83:157-165.
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Yokel RA. 2006. Blood-brain barrier flux of aluminum, manganese, iron and other metals suspected to contribute to metal-induced neurodegeneration. Journal of Alzheimer’s Disease. 10(2-3):223-253.
- Yasir A. Rehman, Ph.D.
Dr. Rehman was born in Rawalpindi, Pakistan. He completed his MSc from PMAS – Arid Agriculture University Rawalpindi in 2011 where his thesis comprised a health risk assessment of subjects living in the vicinity of wastewater channels in urban settings and its relationship with the incidence of Malaria.
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OTHER RESEARCH ON WATER CONTAMINANTS BY DR. YASIR
