Human Exposure to Environmental Chemicals in Drinking Water

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Abstract

This paper focuses on the various effects of excessive concentrations of arsenic, lead, and chlorine in drinking water. While arsenic was originally touted as a remedial substance, that it may actually cause the onset of lung cancer and neurological disorders is now widely known, and herein elaborated upon. The widely reported effects of lead contamination have similarly been disseminated through years of literature, and this paper additionally investigates some of the dangers of lead as regards women in pregnancy, as well as lead’s effects on young children. While potentially purported as an equally dangerous chemical, one might be surprised to learn that much research has been conducted which not only exonerates chlorine as a dangerous compound but supports it as a means of decontamination for drinking water. Finally, this paper discusses some of the recent discoveries and processes currently in use to combat the threat of drinking-water contamination.

Introduction

Contamination of drinking water as a result of exposure to environmental chemicals is a concern that has been increasingly acknowledged in the public forums in recent years. Though many chemicals now established as toxic were once widely prescribed and even cherished for their apparent remedial abilities, increased regulation of such substances has dramatically reduced the negative effects of their consumption. However, a number of lethal chemical compounds such as arsenic, lead, and chlorine continues to contaminate drinking waters of those near industrial worksites, as well as of people in many third world countries. And while none of the aforementioned chemical’s effects are comprehensively understood, many studies assert that ingestion of waters thusly contaminated can result in numerous physical ailments, ranging from cancer and diabetes to various neuropathies and even adverse effects on the health of a fetus.

Arsenic

Arsenic is a naturally occurring chemical substance that has been experimented with by human beings for many thousands of years. It is a substance “widely distributed in nature…usually found associated with the ores of antimony and silver…and as a constituent of many metallic sulfides” (Doyle 309). For nearly 3000 years, the compound has been used for various medicinal purposes in accordance with ancient Chinese medicine, and the Egyptians are toted as having used it in their manipulation of copper, as well as in their embalming fluid (Doyle 309). There is also evidence that Hindu medicinal practices utilized the substance to a great extent, and both philosophers Hippocrates and Dioscórides recommended arseniko as a tonic and as a remedy for asthma, respectively (Doyle 309). In modern times, the majority of commercial arsenic is acquired as a “byproduct of the smelting of copper, lead, cobalt, and gold ores” (Doyle 314), and its uses are still largely associated with medicinal and metallurgical processes.

Despite its commercial applications, arsenic is a tremendously lethal substance that when unknowingly consumed, as a result of contamination, can pose a myriad of health risks. Many studies have shown that “arsenic is linked to bladder, skin, and lung cancer in populations highly exposed to…contaminated drinking water [16,17]” (Lee et al, 2). One study, in particular, showed that “in Florida, clusters of bladder cancer were found among those who live in close proximity to known arsenic-contaminated drinking water wells [29]” (Lee et al, 8). This research clearly seems to indicate a concrete connection between arsenic contamination in drinking water and the onset of cancer. Ultimately, Lee et al’s study concluded that their analysis “identified multiple areas of pancreatic cancer clustering within Florida…[and] identified pancreatic cancer clusters that had an increased likelihood of being located near known arsenic-contaminated wells” (Lee et al, 7). The following image depicts these clusters across the state of Florida (Clown Fish). Other studies that focus on research in lung cancer have found that “Arsenic species directly modulate several oncogenic pathways…and these specific pathways possess actionable targets for therapy in lung cancer (Martinez et al, 8). To put into more simplistic terms, this evidence suggests that arsenic, as a toxin, may not only induce cancerous tumors but also directly affect the pathways employed to treat such conditions. In addition to the cancerous effects of exposure, arsenic is also related to a number of cardiovascular ailments as well.

Much research can attest to the claim that exposure to arsenic from contaminated sources of drinking water contributes to the inception of cardiovascular disease. One study from Giri et al. corroborated this hypothesis, stating that an “arsenic exposed population exhibits…increased likelihood of cardiovascular disease”, and further stated that such prolonged exposure to arsenic also results in increased serum ANA, a compound “present in lower titers in liver diseases” as well (2). Furthermore, the study demonstrated that arsenic exposure resulted in the secretion of a number of cardiovascular markers, explaining that:

“IL6, IL8, and MCP-1 are inflammatory cytokines associated with cardiovascular disease. Thus, we determined the circulating levels of these cytokines as indicators of cardiovascular disease associated with arsenic exposure…and found that IL6 and IL8 were increased significantly in the exposed group.” (Giri et al 5)

This research concluded that there is a considerable amount of evidence which points to the fact that prolonged arsenic exposure does indeed increase the likelihood of cardiovascular disease. Furthermore, nearly all research into the subject of arsenic exposure contends that numerous neuropathies, as well as diabetes, can also be triggered by this substance.

Disorders of the nervous system may constitute some of the worst conditions that prolonged exposure to arsenic can induce. Multiple studies on the effects of arsenic exposure assert that such exposure can result in peripheral, auditory, visual and somatosensory neuropathies (Wade et al, 169). Though perhaps not as life-threatening as cancerous formations, hearing loss, and visual impairment that stem from arsenic exposure can be just as devastating in terms of quality of life for those afflicted. And even despite arsenic’s utilization in the treatment of various forms of leukemia, one study reports that exposure to the substance might have caused the onset of some kind of optical neuropathy, as one patient “noticed a regressive but recurrent impairment of her vision” (Tilly et al, 168). On following up with these complaints, “The Farnsworth 100 hue test revealed a dyschromatopsy in the blue-yellow axis that evokes a toxic neuropathy (Tilly et al, 168). Furthermore, the effects of peripheral neuropathy, loss of sensation in the hands and feet, can have significant impact on one’s ability to work, not to mention the psychological effects associated with the loss of senses that many consider inherent to enjoying life’s journey.

Diabetes is yet another physical ailment that has been linked to extended periods of exposure to arsenic. However, the overarching literature of recent studies remains somewhat inconclusive as to the notion that there is a connection between arsenic exposure and diabetes, (Loomis et al. 1662) at least across rates of exposure. Still, there are other recent studies “designed to focus more specifically on diabetes-relevant endpoints [that] appear, at least qualitatively, to support a link between arsenic exposure and diabetes” (Loomis et al. 1665). To the aid of the latter, another study from the National Toxicology Program found that studies of citizens in countries such as Bangladesh and Taiwan, where drinking water can have as much as 10-15 times the amount of arsenic found in water in the United States, consistently conclude that there is a strong connection between arsenic exposure and diabetes (Ahearn). That there have been mixed results in studies that attempt to establish connections between low to moderate levels of arsenic exposure and diabetes does not validate either side of the argument. For now, it appears that correlations between diabetes and arsenic-contaminated drinking water require further research to be proven valid. Meanwhile, there are other substances, their toxicity so irrefutably demonstrated, that questions regarding their dangers are no longer disputed.

Lead

Lead is another chemical that often taints the purity of drinking waters, resulting in a number of complications for any who find themselves in such situations. Today, the dangers associated with lead are quite common knowledge, but thousands of years ago the compound was considerably less researched. To illustrate the chemical’s longevity, archaeologists have come across lead beads that date back to almost 7000 B.C. (Heskel). By far, however, it was the Romans who first began to mass-produce lead pipes for what some purport to be large-scale plumbing operations (Squatriti 134). And through much of the 1600s, the relative unfamiliarity with lead was often the reason that it was rarely ever distinguished from tin (Polyaskiy). However, since the 17th century, much scientific progress has been made in the field of chemistry as pertains to lead. Now, the advent of lead is even more pronounced, with one author estimating that the “modern man’s lead exposure is 300 to 500 times more than background or natural levels (Kitman 14). Such a statistic is not to be taken lightly, as overexposure to lead from contaminated drinking water is often the onset of a number of conditions that not only affect the subject but may also have negative implications for a fetus in the womb.

The potential health risks that stem from an abundance of lead in the body are quite diverse. The range of effects from such contamination includes “listlessness, bizarre behavior, incoordination, vomiting…and even coma and death” (Farley). The most common cause of lead poisoning in children is associated with interactions involving lead paint. Because young children frequently explore with their mouths, they can easily become poisoned from “chronic ingestion of lead paint chips and house dust or soil that may have lead particles in it” (Farley). Even more detrimental than what children ingest in the early stages of their childhood, however, may be the lead contamination present in the body of his or her mother during pregnancy.

A fetus may experience a wide variety of health-related difficulties as a result of lead contamination during pregnancy. Despite what many studies purport, however, many children with high lead exposure do not develop ADHD (Banerjee, Middleton, and Faraone, 1269). What is considerably more certain, though, as many studies have demonstrated, is that children exposed to high amounts of lead often suffer from hyperactivity and distractibility (Banerjee, Middleton, and Faraone, 1269). According to one article, a fetus’s exposure to lead, even to levels deemed safe for children “appears to slow important aspects of mental development in the first two years of life” (Bower). This same article further reported that in one study of low-income inner-city pregnant women, low-level exposures to lead increased the probability of children with “low birth weight and somewhat slowed neurological development” (Bower). Additionally, other studies focus on the intellectual capacity of children that, as fetuses, were subjected to lead-rich substances. One pediatric study found that “IQs dropped as much as 7.4 points as blood-lead levels (BLLs) rose from 0 to the top of the safe range—10 micrograms (mcg) per deciliter of blood” (Harrar and Poust). Furthermore, it is important to note the study further suggested that “higher lead exposures cut IQs further, but early, low exposure caused the most damage” (Harrar and Poust). Despite the researcher's counterintuitive claims, it seems that above all, children affected by above-average blood-lead levels are more susceptible to impaired cognitive functions later in life.

Chlorine

Chlorine has, in its more common form of sodium chloride, been found in the remnants of societies dating back thousands of years. There has been evidence of rock salt being used as early as 3000 BC, but it wasn’t until 1630 that chlorine was recognized as a gas by Belgian chemist Jan Baptist van Helmont (Greenwood). And while chlorine originally confounded scientists—they could neither conclude whether it was an element or a compound—in 1810 Sir Humphry Davy conclusively discovered that it was, in fact, an element (Weeks). More recently, however, the subject of chlorine is generally in the context of its role in potable water, and what health risks, if any, it poses to human beings.

Water is often treated with mild amounts of chlorine for the purpose of disinfection. And while “chlorine can indeed disinfect a well…it can be dangerous in the hands of anyone but a skilled professional” (Ebbert and Meyers). It appears, though, that the benefits of water chlorination, for the purpose of disinfection, far outweigh any potential drawbacks of such a process. In fact, one study on a cholera outbreak in Ghana described how researchers, when confronted with the epidemic, were able to curb the outbreak by either boiling local water supplies or chlorinating them (Odei et al., 122). It should be understood, however, that the ingestion of any compound in excess will surely result in the body reacting adversely. As it stands, though, chlorinating water has been largely to the benefit of many societies that were historically decimated by diseases of dysentery.

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