Table of Contents
Background
Lead (Pb) is a heavy metal that is found naturally in the environment through various processes such as weathering of lead-containing minerals and the release of Pb from volcanoes. However, its major spread in the environment is through human activities mainly associated with fossil fuel burning, industrial processes, and the use of lead-based products. Some other activities that can contribute to Lead Pb pollution include mining, smelting, and the use of Pb-based paints, pesticides, and other products. Lead can enter and contaminate drinking water in many ways mainly including contact with pipes, fittings, or other plumbing materials that contain Lead. This is more likely to occur in older buildings or homes with lead pipes, or in areas where the water has high acidity or low mineral content. If drinking water comes into contact with lead-based paint that has deteriorated or been damaged, it can leach lead into the water. This can happen if water pipes pass through walls or other surfaces that are painted with lead-based paint.
Pb can also enter drinking water if it is present in the soil or water near industrial or agricultural sites, where it may be used in manufacturing processes or applied as a pesticide from there it may contaminate ground and surface water reservoirs through leaching and run-off processes respectively. Moreover, if a water treatment plant does not use appropriate techniques or equipment to remove Lead from the water, it can remain in the water supply. In some cases, the pipes that connect a water main to a home or building may be made of Lead. If this is the case, Lead can leach into the water as it passes through the pipes. In the US, the quality of drinking water is ensured through the implementation of the federal Safe Drinking Water Act (SDWA). The EPA is the main regulatory body that is responsible for setting standards for contaminants in drinking water and their enforcement in public water systems. For this, the EPA has set a maximum contaminant level (MCL) for lead in drinking water at 15 parts per billion (ppb). This ensures that the level of Lead in drinking water should not exceed 15 ppb to avoid any Pb-associated health complications.
Lead-induced toxicity in humans is well documented in the literature which can cause serious health problems, particularly among young children and pregnant women who are considered the most vulnerable age group to metal toxicity. Long-term exposure to Lead can cause damage to the brain, nervous system, and other organs. Lead can interfere with the body’s ability to absorb calcium, leading to weak bones and osteoporosis. Further, cardiovascular and reproductive system problems and kidney damage have also been significantly associated with chronic Lead exposure. Moreover, acute exposure to Lead at high concentrations is also a cause of concern which can lead to health problems such as vomiting, diarrhea, seizures, and even death.
Given the toxicity of Lead, since EPA has regulated this contaminant to ensure a safe drinking water supply to US residents, therefore, it is necessary to reduce your exposure to Pb by using an appropriate water filter or removal technique in your drinking water. If you have any concerns related to the Lead contamination in your drinking water, this can be tested through a local water utility or contact EPA to find out more information. You can also have your water tested by a certified laboratory to determine the Pb level. If the Pb level in your water exceeds the MCL, you should take steps to reduce your exposure to Lead by using a water filter or bottled water for drinking and cooking.
Being a potent neurotoxin, Lead (Pb) can adversely impact most organ systems inside the human body. It also has the potential to disrupt development in young children even at very low concentrations (Aizer and Currie 2019). Federal regulations related to Pb levels in various items such as paint, gasoline, and plumbing have resulted in a dramatic reduction in the incidence of acute Lead poisoning in the US (Triantafyllidou et al. 2014; Tsoi et al. 2016). Despite this, regular monitoring and testing for lead in schools drinking water is still warranted given the established scientific evidence associated with human health in relation to Pb exposure. These toxic effects of Lead are mainly due to its ability to interfere with the normal functioning of a number of enzymes and proteins in the body (Engwa et al. 2019).
One of the main mechanisms of Lead toxicity underlies its ability to disrupt the function of calcium channels in cells, which are important for transmitting signals between cells (Bressler and Goldstein 1991). Lead (Pb) also possesses the ability to interfere with various enzyme activities involved in the metabolism of proteins, carbohydrates, and lipids, leading to a variety of metabolic abnormalities (Gillis et al. 2012). In addition to these biochemical effects, Lead can also have cellular effects, such as disrupting the normal division and differentiation of cells, leading to abnormal tissue development (Huang and Schneider 2004). Furthermore,
Pb can also cause oxidative stress and inflammation, leading to DNA damage and cell death (Dobrakowski et al. 2017). Overall, the toxic effects of Pb are due to its ability to disrupt a wide range of cellular and molecular processes in the body, leading to a variety of harmful health effects. Omics-based findings on occupationally exposed subjects to Pb have revealed is the impact on altered DNA methylation providing evidence of epigenomic changes associated with Pb (Zhang et al. 2019). However, epidemiological data on human exposure to Pb through drinking water using OMICS platforms is still missing and demands further research to address molecular mechanisms associated with Pb toxicity.
Detection Methods and Removal Strategies
Several methods are available for quantifying Lead in drinking water. The choice of preference of these methods is based on affordability and desired results. There are several testing kits now available through which, the Lead (Pb) estimation can be performed at home by the consumers. For Laboratory analysis, it is necessary to take a freshly collected water sample and send it to the laboratory for analysis. Among the known Pb quantification methods include colorimetric methods to get estimated information related to Pb levels. However, for more accurate and sensitive quantification of Pb, AAS coupled with different detection systems i.e. FAAS, GFAAS, etc. as well as ICP-MS/OES have been widely used quantification methods for metals. AAS-based methods use a beam of light to measure the absorption of Lead in a sample. Whereas, ICP uses a plasma torch to vaporize the sample and quantify Pb in the sample through its attached detectors.
To quantify the ionic species of Pb in drinking water, ion chromatography is used, and to measure the organic compounds chelated with Pb in water, mostly high-performance liquid chromatography (HPLC) is coupled with AAS or ICP for simultaneous detection of Pb and its organic metabolites. It is important to note that once Lead (Pb) is detected in drinking water, a serious challenge arises related to its efficient removal to ensure Pb-free drinking water to the consumers. For this, several methods are available and can be adapted based on affordability and efficiency. The most widely used method to remove Pb includes reverse osmosis which allows water to pass through a semipermeable membrane with pressure resulting in the removal of Pb from drinking water (Lin et al. 2014).
Recently, biochar made from agricultural products has been found very effective for the removal of Lead and Cd (Puglla et al. 2020). Moreover, an activated carbon-based method that uses a filter made of activated carbon is also very effective in removing Pb by absorbing Pb impurities in drinking water (Zuo et al. 2021). Other Pb removal methods include ion exchange which involves passing water through a bed of resin beads charged with ions exchanging ions present in water resulting in efficient removal of Lead (Chanthapon et al. 2018). At a smaller scale, distillation can also be used in which water is heated until it turns into steam which is then collected and cooled, resulting in pure water removing variety of contaminants including Lead (Pb).
Public Perspective
Following frequently asked questions (FAQs) try to address some general public concerns in the US, especially the NYC region.
Pb can cause serious health problems if its high amount is consumed by your body from drinking water or other sources. This may result in damage to the brain and kidneys and can interfere with the production of red blood cells that carry oxygen to all parts of your body.
The CDC suggests two cost-effective ways of Pb removal from drinking water i.e. Reverse Osmosis or Distillation. Reverse osmosis is a simple and economical way to protect your household drinking water by filtering out contaminants like Pb. Reverse Osmosis has the potential to remove up to 99.1% of Pb in water.
Elevated and chronic Pb exposure may result in multiple health issues such as anemia, weakness, and kidney and brain damage. The associated symptoms may comprise abdominal pain, Constipation, lethargy, Headache, Irritation, appetite and memory loss, and pain or tingling in limbs.
Since Pb pipes aren’t used in the production of bottled water, the FDA has set the limit for lead in bottled water at 5 ppb (parts per billion). The FDA’s bottled water quality regulations require bottled water companies to regularly sample and analyze their water.
The rate of excretion of Pb from the body is dependent on the duration of exposure to the contaminant. If the Pb is not excreted by the kidney or gut within a few weeks the remaining Pb moves to your bones and teeth. Some Pb amounts can be stored for up to 30 years in bone.
Chelation is one medication-based method to remove Pb from the body. In this method, the given medication is taken orally binds with Pb and excretes through urine. Chelation therapy might be recommended for children with a blood level of 45 mcg/dL or greater and adults with high blood levels of lead or symptoms of lead poisoning.
Reverse Osmosis (RO) systems are capable of removing 94% to 97% of Pb from water.
Pb poisoning in the body can be tested through the capillary blood sample method which uses a finger prick to take a small amount of blood sample and is relatively a simple and easy way to test water for high lead levels.
Once Pb is in the body, it can also be stored in bone for years. Even after exposure stops, the Pb can come back into the bloodstream and continue to damage the brain and other organs for years to come.
Vitamin C has been consistently linked to lower blood Pb levels and minimizes the risk of organ damage by inhibiting Pb uptake at the cellular level thereby reducing lead’s toxicity to some organs.
Conclusion
Lead (Pb) is a toxic metal that can have serious health effects when exposure is for long period. Drinking water exposure to Pb has been associated with various health problems when its higher concentration (>MCL) is consumed chronically. Various sources have been identified so far causing increased levels of Lead in drinking water. Identification of hotspot regions of Lead contamination in the US and their regular monitoring along with efficient removal through effective treatment technology has been a serious challenge for authorities during recent years.
Furthermore, to estimate the uptake of Lead by humans through drinking water consumption, cross-sectional biomonitoring studies must be conducted across States correlating drinking water Lead (Pb) levels with human biological specimens i.e. blood, urine, nails, etc. for in-depth risk assessment of Lead exposure.
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- 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
