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 Table of Contents  
REVIEW ARTICLE
Year : 2017  |  Volume : 2  |  Issue : 1  |  Page : 9-21

Medical geology of arsenic in groundwater and well water in Southeast Michigan


Department of Public and Environmental Wellness, School of Health Sciences, Environmental Health and Safety Program, Oakland University, Rochester, Michigan 48309, USA

Date of Submission18-Jan-2017
Date of Acceptance14-Feb-2017
Date of Web Publication19-Apr-2017

Correspondence Address:
Richard Olawoyin
Department of Environmental Health and Safety, Oakland University, Rochester, Michigan 48309
USA
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ed.ed_1_17

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  Abstract 

Arsenic concentrations exceeding the Environmental Protection Agency's (EPA) maximum containment level (MCL) of 10 μg/l are frequently reported in groundwater and well water in Southeast (SE) Michigan. The following research examined the relationship between arsenic exposure in well water and groundwater in SE Michigan and several adverse health effects including cancer, diabetes mellitus, cerebrovascular disease, and kidney disease. The expected outcome was to prove that arsenic exposure is a problem in the area while addressing mitigation strategies and technologies needed to reduce exposure. The objective of this research was to propose effective methods and strategies to help mitigate and reduce the risk of arsenic exposure for the population in SE Michigan. Reducing arsenic concentration in well water and groundwater will help reduce adverse health effects as well as keep drinking water safe for residents in the area. Relevant data about the geology of the area and epidemiological studies of arsenic-related disease and mortality rates proved the increased incidence of diseases related to arsenic exposure in the area. The population demographic data and arsenic exposure data were analyzed. The data collected demonstrated that residents in SE Michigan are exposed to elevated arsenic concentrations in well water and groundwater that exceed the EPA MCL. The elevated levels of arsenic in well water and groundwater are due to the mobilized inorganic arsenic in the bedrock aquifers in SE Michigan. The findings from the research show that arsenic, even at low levels, is harmful to human health. Mitigation strategies discussed include legislative action, systems for removing arsenic from water, adopting improved well-drilling practices, education, using bottled water, and more. Implementing these controls would increase the health and quality of life for residents of SE Michigan.

Keywords:  Arsenic, arsenic contamination, arsenic mobilization, geology, groundwater, medical geology, Southeast Michigan, well water


How to cite this article:
Asher M, Cleary E, Olawoyin R. Medical geology of arsenic in groundwater and well water in Southeast Michigan. Environ Dis 2017;2:9-21

How to cite this URL:
Asher M, Cleary E, Olawoyin R. Medical geology of arsenic in groundwater and well water in Southeast Michigan. Environ Dis [serial online] 2017 [cited 2021 Nov 27];2:9-21. Available from: http://www.environmentmed.org/text.asp?2017/2/1/9/204788




  Introduction Top


Arsenic is a naturally occurring constituent of the earth's crust and is distributed environmentally in the air, water, and land. People are exposed to elevated levels of arsenic through contaminated drinking water, using contaminated water for food preparation and irrigation of crops, and industrial processes.[1] Arsenic levels tend to be higher in drinking water that comes from ground sources, such as wells.[2] The Michigan Department of Environmental Quality (MDEQ), the Michigan Department of Community Health (MDCH), and the United States Geological Survey have indicated that several counties in Southeast (SE) Michigan exceed the Environmental Protection Agency's (EPA) maximum containment level (MCL) of 10 μg/l for drinking water in groundwater and well water, making this an issue that must be addressed.[3]

Arsenic is often found in the environment combined with oxygen, chlorine, and sulfur. In this state, it is referred to as inorganic arsenic. In the past, inorganic arsenic was used for pesticides but can no longer be used in agriculture. In the environment, arsenic cannot be destroyed; it can only change its form or become attached to or separated from particles.[4] Arsenic compounds dissolve easily in water, thus getting into lakes, rivers, or underground water by dissolving in rain or snow [Appendix [Figure 1].

Arsenic contamination in groundwater and well water in Michigan is a cause for concern. In 1997, fieldwork conducted in Huron, Tuscola, Sanilac, Lapeer, Genesee, Shiawassee, Livingston, Oakland, Macomb, and Washtenaw Counties found that 68% of the sampled wells exceeded the EPA minimum concentration levels (MCLs) of 10 μg/l, and the average concentration was 29 μg/l [Appendix [Figure 2].[5] In 2003 and 2004, individuals living in SE Michigan ingested about 11–24 μg/day of inorganic arsenic, which is above the average of 6 μg/day.[6] The International Agency for Research on Cancer (IARC) classifies inorganic arsenic as carcinogenic to humans, particularly putting individuals at risk for lung, bladder, and skin cancer.[2] Therefore, residents of SE Michigan are at higher risk for lung, bladder, and skin cancers due to elevated groundwater and well water arsenic concentrations exceeding the EPA MCL of 10 μg/l.

Literature review

Various health effects of arsenic are explored and arsenic in groundwater in SE Michigan is explored. It is hypothesized that residents of SE Michigan are affected by the levels of arsenic in the groundwater that they drink and that arsenic is a significant problem in the area. A critical review of existing literature attempts to support this notion.

Noncancerous health effects

Ongoing exposures to arsenic continue to be a significant threat to public health. Arsenic in drinking water, which is the focus of this review, is usually in the inorganic form.[7] Arsenic is the highest ranking in the United States ATSDR 2015 substance priority list; this means that this substance is commonly found and poses the most significant potential threat to human health.[8] When considering toxicity, the IARC lists arsenic as a Group I known human carcinogen that also induces a wide range of other noncancerous effects; essentially no bodily system is free from potential harm.[7]

Arsenic can induce a variety of respiratory effects. Mortality from pulmonary tuberculosis was increased in individuals exposed to arsenic in drinking water in a Chilean cohort study; the findings are biologically plausible in light that arsenic is an immunosuppressant and a cause of chronic lung disease.[9] Early-life exposure to arsenic in drinking water could have permanent respiratory effects similar in magnitude to smoking throughout adulthood. A study found that early-life exposure was associated with 11.5% lower forced expiratory volume, 12.2% lower forced vital capacity, and increased breathlessness.[10] The cardiovascular system is also affected by arsenic exposure. A dose–response assessment including six studies with available data showed an increasing trend in the odds of hypertension with increasing arsenic exposure.[11] Arsenic exposure also affects the immune system by impairing the function of several key immune cells. A toxicology study analyzed the effects of inorganic arsenic found in drinking water on T-cell proliferation and cytokine expression. The study found that arsenic inhibits T-cell proliferation and alters the balance of cytokines secreted by co-stimulated T-cells.[12]

Arsenic is also an endocrine disruptor. Arsenic is a strong endocrine disruptor at low, environmentally relevant levels and alters steroid signaling at the level of receptor-mediated gene regulation for steroid receptors. Arsenic can also disrupt gene regulation through retinoic acid receptor (RAR) and thyroid hormone receptor (TR) at very low concentrations. RAR and TR are essential for normal human development and adult function, and dysregulation leads to diseases and developmental risks.[13] Neurological impairments are also associated with exposure to arsenic. Arsenic in drinking water has been associated with impaired cognitive function in school-aged children. A population-based longitudinal study found adverse effects of arsenic exposure on intelligent quotient (IQ) in girls.[14] Another study found an adverse association between arsenic exposure and motor function in children. Children exposed to arsenic around the world have been documented as having poorer cognitive function, deficits in verbal skill, and lower IQ.[15] These findings suggest that arsenic impacts health negatively in a variety of ways and mechanisms and that exposure to arsenic is a major health issue today.

Cancers associated with arsenic exposure

Epidemiological studies and case reports of humans exposed to arsenic have shown that exposure to arsenic and its inorganic compounds increases the risk of cancer. Cancer tissue sites include the skin, lung, digestive tract, liver, urinary bladder, kidney, and lymphatic and hematopoietic systems.[16] Long-term exposure to inorganic arsenic from drinking water has been shown to induce cancers in lung, urinary bladder, kidney, liver, and skin in a dose–response relationship. Oxidative stress, chromosomal abnormality, and altered growth factors may be modes of action in arsenic carcinogenesis. Many studies have shown an association between skin cancer and exposure to arsenic in drinking water. Common skin cancers induced by arsenic exposure include Bowen's disease, basal cell carcinoma, and squamous cell carcinoma.[17] A study assessing skin cancer occurrence in the United States found that squamous-cell and basal-cell carcinomas occurred in those individuals in the top 97th percentile of toenail arsenic concentrations.[18]

Lung cancer is also an outcome of arsenic exposure. In a United States population-based case-control study, the carcinogenic potential in arsenic in areas with low-to-moderate concentrations of arsenic in drinking water was explored. Arsenic exposure was associated with small-cell and squamous-cell carcinoma of the lung. There was an elevated risk of lung cancer in participants with a history of lung disease and toenail arsenic.[19] Several epidemiologic studies have also shown that arsenic exposure from drinking water is linked to increased urinary cancer risk; this includes the bladder and kidney.[20] A study explored that arsenic in drinking water ingested by children may increase the risks of childhood liver cancer mortality. It was found that liver cancer mortality was significantly increased for both sexes from ages 0 to 19 years for those exposed to arsenic.[21] It can be strongly concluded that cancer is an outcome of arsenic exposure.

Arsenic in Southeast Michigan

High concentrations of naturally occurring arsenic have been found in the groundwater in SE Michigan. One study investigated the distribution of arsenic species and their redox chemistry in groundwater to evaluate possible arsenic dissolution mechanisms. Total arsenic concentrations and the ratios of As (III) to As (V) were found for groundwater in SE Michigan. Ten counties in SE Michigan were included in this study [Figure 1].
Figure 1: Map showing location, geology, and sampling sites of the study area[5]

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Arsenic concentrations ranged from 0.5 to 278 μg/l, with the average of 29 μg/l. About 53%–98% of the arsenic detected was arsenite (As [III]). In shallow groundwater (< 15 m), arsenic concentrations are low probably due to the formation of insoluble ferrosoferric hydroxide complex.[5] In deep groundwater (>15 m), the concentration of arsenic may be controlled by reductive dissolution of arsenic-rich iron hydroxide or oxyhydroxide and dissolution of arsenic sulfide minerals.[5] Arsenic concentrations above 10 μg/l are often reported in groundwater from bedrock and unconsolidated aquifers of SE Michigan [Appendix [Figure 3]; 10 μg/l is the United States maximum contaminant level and the World Health Organization value.

[Additional file 1]

A study aimed to investigate the relationship between dissolved arsenic concentrations, reported groundwater recharge rates, well construction characteristics, and geology in unconsolidated and bedrock aquifers. Conditions for arsenic mobilization can be found along the bedrock-unconsolidated interface, including changes in reduction/oxidation potential and enhanced biogeochemical activity due to differences between geologic strata. These results help understand arsenic mobilization and can be used to guide well construction practices in SE Michigan.[22] A population-based case–control study in SE Michigan was conducted where 230,000 people were exposed to arsenic concentrations between 10 and 100 μg. It was found that arsenic exposure levels >10 μg/l in individuals between 30 and 55 years with above average water consumption were associated with the development of bladder cancer.[23] In another study, two drinking water samples were taken an average of 14 months apart for 261 individuals enrolled in a case–control study of arsenic exposure and bladder cancer in SE Michigan. The drinking water came from private wells, public water supplies, and bottled water. Mean arsenic concentrations were highest in private wells and lowest in bottled water samples. Measurement reproducibility did not vary by type of point-of-use (POU) device such as softener, filter, or reverse osmosis system. Arsenic concentrations differed between samples treated with POU devices and untreated samples taken on the same day. Substantial differences in arsenic concentrations were regularly observed for reverse osmosis systems. These results show that while a single residential arsenic measurement can be used to represent exposure in this region, researchers should get information on changes in water source and POU treatment devices accurately portray exposures over time.[24]

It can be concluded that arsenic in water in SE Michigan is an issue and that more needs to be done to fully understand what impacts the mobilization of arsenic in water and what geological features influence this exposure. More also needs to be understood on identifying those at risk and how to best characterize this risk.

Current interventions

Interventions are needed to combat this global problem; over 200 million people are at risk for exposure to arsenic levels that are harmful to health.[7] Arsenic in SE Michigan is one area where interventions are needed to prevent potential harmful health effects. One study in the United States aimed to measure the effectiveness of a bottled water intervention to reduce arsenic exposure. It was found that providing arsenic-free bottled water modestly reduced urinary total inorganic arsenic.[25] Another study demonstrated that a household-level arsenic educational program could be used to significantly increase arsenic awareness.[26] One study found that geological and environmental factors could be used to predict occurrence of higher levels of arsenic concentrations in unregulated private water wells and also higher levels of toenail arsenic.

Geological and environmental factors are also associated with individual arsenic body burden. This approach can be used to help design intervention strategies to reduce arsenic body burden and diseases caused by arsenic.[27] A study sought to explore the impact of New Jersey legislation on private well testing and treatment. The required testing significantly increased arsenic testing rates, allowed for the identification of more wells with arsenic, and resulted in more treatment for arsenic contaminated water. Required arsenic testing can reduce socioeconomic disparities and benefit children. To maximize benefits, more support for households after testing is necessary.

This review supported the hypothesis that exposure to arsenic is a significant health risk, even at low levels. Arsenic has many noncancerous and cancerous health effects and more needs to be done to combat this issue. Arsenic is present at concerning amounts in SE Michigan. This signifies the need for interventions and strategies to lessen the impact and reduce the risk that arsenic poses to the people residing in this area.

Specific aims of the current research

The current work addresses the arsenic problem in SE Michigan, with aims of reducing exposure and risk to arsenic for SE Michigan residents. This is done by exploring the potential influences that contribute to this issue. Designing an effective intervention program is essential for positively impacting public health. This will be done by understanding the geological, socioeconomic, and biological factors influencing this problem. By understanding the influencing factors correct, effective interventions can be recommended for the population that resides in the area.

Specific aims of the research are to address gaps in understanding how arsenic is mobilized in SE Michigan and its sources; this will be done by looking holistically at what research has been done. A specific aim is to find the most applicable interventions for those residing in SE Michigan. The next specific aim is to reduce the dose and exposure of concentrations by recommending the application of the most valuable interventions for improving health and reducing the arsenic problem. Another specific aim is to make sure to address low-level exposure, not just exposure above limits, as metabolites of arsenic are often more toxic and there is no differentiation in this in the current standards. The last specific aim is to propose the adoption of required testing for private wells and to incorporate regular testing in the area.


  Geology of Southeast Michigan Top


The Michigan Basin dominates the geology of Michigan, which is an elliptical basin that occupies approximately 80,000 square miles and covers all of the Lower Peninsula. The Michigan Basin consists mostly of shale, limestone, and sandstone and is estimated to be about 14,000 feet thick.[28] Michigan's rocks are the result of the pre-Cambrian age (approximately 3900 million years ago), and the state's metallic mineral sources include iron, copper, copper sulfides, and silver.[29] The sedimentary rocks deposited in the Michigan Basin were deposited during the late pre-Cambrian through Pennsylvanian time. Jurassic red beds and Pleistocene glacial deposits cover the sedimentary rocks with thickness that varies between a few feet to over 1200 feet.[30]

The state of Michigan lies within the heart of the Great Lakes Basin. The Great Lakes Basin occupies approximately 5500 cubic miles and formed through the process of episodic glaciation. The Great Lakes Basin is the watersheds that drain into the Great Lakes and includes about 85% of North America's and 20% of the world's surface fresh water.[31] The southern region is underlain by relatively soft, Paleozoic sedimentary rocks and includes the Lake Erie, the Lake Michigan, the Western portion of Lake Huron, and a portion of the Lake Ontario Basins [Figure 2].[32]
Figure 2: Topographic map of Southeast Michigan[32]

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The state of Michigan has sufficient supplies of water that can be reached by digging wells into the surface layers of glacial material or down into the aquifers. The sedimentary rock aquifers are good storage areas for water and can be drilled for domestic and industrial water supplies.[33] The majority of Michigan's water wells are shallow and can easily be pumped from surface sands and gravels deposited by glaciers. Much of the groundwater in the Lower Peninsula comes from glacial deposits and is “hard” due to the lime (CaCO3) concentration held in the solution. There is also a tremendous supply of water from Lakes Superior, Michigan, Huron, and Erie.

Most wells used for drinking water in SE Michigan are in the Mississippian Marshall Sandstone, which is the main bedrock aquifer in the region. The Marshall formation overlies the Mississippian Coldwater Shale and is about 300 feet thick and is comprised quartz grains embedded in a softer cement of mica, siderite, and clay.[34] The water in the Marshall Sandstone is fresh at the edges of the Michigan Basin, making it a very good freshwater aquifer.

Prevalence of disease or illness attributable to geology

One study found that in SE Michigan, namely Genesee County where concentrations of arsenic in water are higher, there was an association between low-level arsenic exposure and ischemic stroke admissions in an adjusted analysis. There was a significant trend when arsenic was modeled based on quintiles of distribution and found a negative association between arsenic and nonvascular outcomes. The study found that the association between arsenic and stroke might be most apparent at more elevated levels of arsenic such as those in Genesee County. This arsenic comes from the unconsolidated and bedrock aquifers throughout SE Michigan.[35]

Another study conducted a standardized mortality ratio (SMR) analysis for six counties in SE Michigan to explore the relationship between moderate arsenic levels and 23 selected disease outcomes. These disease outcomes were many types of cancer, diseases of the circulatory and respiratory system, diabetes mellitus, and kidney and liver diseases. Arsenic data were collected from 9251 wells tested by the MDEQ from 1983 to 2002. Michigan death files data were compiled from 1979 to 1997. The six-county study had population-weighted mean arsenic concentration of 11.00 μg/l. Elevated mortality rates were observed in both males and females for all diseases of the circulatory system, cerebrovascular diseases, diabetes mellitus, and kidney diseases. This study suggests that exposure to low-to-moderate levels of arsenic in drinking water may be linked to many of the leading causes of mortality.[36]


  Method of Study Top


Significance of study

There are 2.8 million people, 1.6 million of which rely on groundwater as their drinking water source.[22] Of those, approximately 230,000 people in SE Michigan are exposed to arsenic at levels >10 μg/l; the source of this exposure is drinking water. Therefore, the SE region is one of the densest populated regions of moderately elevated arsenic exposure in the United States. With levels frequently exceeding the maximum contaminant level set by the EPA, solutions are needed to rectify the arsenic problem in this geographic location. With elevated levels of arsenic in drinking water being associated with skin ailments, cancer, diabetes, and vascular diseases, those populating the region may suffer some of these health effects.[35] Mechanisms for arsenic mobilization and transport have not all been identified in the SE region of Michigan.[22] The research aims to provide solutions and identify sources of exposure to arsenic in groundwater and well water. Holistically looking at the arsenic problem encountered in this region will allow for new, innovative solutions and insights into arsenic contaminated water.

Outcomes of the research strategy for arsenic in drinking water will include recommendations for the implementation of mitigation strategies to reduce arsenic levels in groundwater and well water in SE Michigan. In addition, outcomes will also include increased resident awareness of the short- and long-term risks of arsenic consumption with help from the MDCH to ensure that the population of SE Michigan is informed about arsenic toxicity. The fundamental goal is, for the MDEQ, to adopt continuous monitoring strategies as well as effective technology to ensure that the arsenic levels are below the MCL for all residents in SE Michigan.

The results of this research may propose the development of new applicable technology or intervention strategies to reduce arsenic concentrations in groundwater and well water. In addition, the results of the study will be used to reduce arsenic concentrations in groundwater and well water statewide. The research strategy suggests that through effective technology, mitigation strategies, and community awareness, exposure to arsenic in drinking water and arsenic-related diseases in the area will ultimately decrease. These outcomes will greatly impact those in the state that has arsenic-contaminated groundwater or well water as their primary source of drinking water.

Approach

A review of literature on arsenic and arsenic in SE Michigan was conducted to identify existing problems, understand the scope of the issue, and identify areas that must be addressed. The health issues related to arsenic were also examined. Population demographics for SE Michigan were examined including age, race, household income, poverty, and highest level of education to form a holistic view of the people residing in this region. Data and statistics for this area were drawn from various sources including the SE Michigan Council of Governments (SEMCOG). Arsenic levels in the groundwater were also examined along with the geology of the area. Looking at the aforementioned information together provides a holistic view of the population, geology, and arsenic problem and possible related health issues for SE Michigan.

Innovation

The approach taken was unique due to the holistic view that weighed various components of the earth and the population. This includes not only looking at the geology of the area but also looking at the population, their characteristics, and health ailments. Doing this allows to not only look at the arsenic problem due to the geology of the area but also what factors may contribute to this being a health concern. Looking at demographics helps synthesize what drives the people residing in this area to drink groundwater versus bottled water. It may be a lack of education, a noncommunicated risk, or a lack of financial resources. Understanding all these elements allows for unique solutions to address arsenic in groundwater in SE Michigan. Innovative solutions, including the newest advancements and technologies, are given to combat this issue. This holistic approach is favorable because there is a greater likelihood for a significant impact when multiple variables are considered.

Targeted/planned enrollment

The targeted population for the study of arsenic contamination in groundwater and well water is the individuals living in SE Michigan. This population encompasses a wide demographic of individuals that would benefit from this research. According to the SEMCOG, there is an estimated total population of 4,725,876 individuals living in SE Michigan in 2016. The total population in the 2010 census was 4,704,809 people, indicating a 0.4% increase in population.[37] These figures combine population data from Livingston, Macomb, Monroe, Oakland, St. Clair, Washtenaw, and Wayne Counties.

The population represented in the total number of individuals in the 2010 census is comprised the following demographics: 68.5% were light-skinned, 21.6% were dark-skinned, 3.6% were Asian, 2% were multiracial, and 3.9% were Hispanic. In the 2010 census of SE Michigan, the median age was 38.7 years. The average births between 2006 and 2010 were 59,650 and the average deaths were 41,023. The senior and youth population for the 2010 census was comprised the following: 610,665 were 65 years and over; 1,131,035 were under 18 years; 848,195 were 5–17 years; and 282,840 were under 5 years.

The demographics in SE Michigan are diverse when it comes to socioeconomic status. In the 2010 American County Survey 5-year estimates, the medium household income (in 2010 dollars) was $53,242. The number of persons in poverty was 668,869 in 2010, which was 14.3% of the total population of SE Michigan. In March 2015, the unemployment rate was as follows: 3.5% in Ann Arbor, 6.0% in Detroit-Warren-Livonia, 6.3% in Flint, and 4.7% in Monroe [Figure 3].[38],[39]
Figure 3: combined statistical area of SE Michigan for the 2012 economic census. Source: (Economics and Statistics Administration U.S. Census Bureau, 2012)[39]

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Demographic figures and tables

[Figure 4] shows the breakdown of population change by the county in 2010 and 2016, and [Figure 5][40] illustrates the population by gender in SE Michigan in 2014. [Figure 6][41] illustrates the average per capita (per person) income and median household income for SE Michigan.
Figure 4: Population change by the county in Southeast Michigan, 2010–2016. Data source: SEMCOG, 2016

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Figure 5: Population by gender in Southeast Michigan, 2014. Data source: Detroit Regional Chamber, 2016

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Figure 6: Income, per capita and median household, 2014. Source: Detroit Regional Chamber, 2014

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  Results Top


Results of analysis

Data analysis is a crucial process in assessing arsenic exposure risk in SE Michigan and will be evaluated in this section. [Figure 7] illustrates arsenic concentration (μg/l) in water drawn from bedrock wells in SE Michigan, and [Figure 8] illustrates arsenic concentrations (μg/l) in water drawn from unconsolidated wells. Arsenian pyrite and arsenic-rich iron oxyhydroxides are found in unconsolidated deposits, and arsenian pyrite is found in the Marshall sandstone bedrock.
Figure 7: Arsenic concentration (μg/l) in water drawn from bedrock wells in Southeast Michigan. Source: Meliker et al., 2009

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Figure 8: Arsenic concentration (μg/l) in water drawn from unconsolidated wells in Southeast Michigan. Source: Meliker et al., 2009

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Arsenic in the area may be mobilized from unconsolidated material by recharging water and then transported into bedrock aquifers.[22] Arsenic concentrations in these wells exhibited a nonnormal distribution, with most of the concentrations below 10 μg/l, so log-normal arsenic values had to be used.[22] The highest geometric mean arsenic concentrations came from wells from the Coldwater Shale and the Saginaw formation for bedrock and unconsolidated wells, respectively. The highest arsenic concentration sampled was 161 μg/l and came from a bedrock well in the Coldwater Shale. These data show that elevated levels of dissolved arsenic appear in bedrock and unconsolidated wells in SE Michigan.

[Table 1] shows the demographic characteristics of bladder cancer cases in controls in SE Michigan. Cases and controls were enrolled between 2002 and 2006. [Table 1] displays the demographic characteristics of bladder cancer cases and controls in SE Michigan. Males had a larger bladder cancer distribution with 315 cases, and women had 96 cases. 229 cases consumed water at home exceeding 1 l/day, 213 cases had water come from a public water supply, and 198 cases had their water come from a private well. Furthermore, 115 cases with bladder cancer were exposed to arsenic at their residence exceeding 10 μg/l over their life course. This data shows a relationship between low-level arsenic exposure and bladder cancer.
Table 1: Demographic characteristics of bladder cancer cases and controls in SE michigan

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[Table 2] shows exposure data for six counties in the thumb area of Michigan. Arsenic data were collected from 1983 to 2002 and were provided by the MDEQ. [Table 2] and [Figure 9] display arsenic exposure data for the following counties in SE Michigan: Genesee, Huron, Lapeer, Sanilac, Shiawassee, and Tuscola. The population-weighted mean arsenic concentrations for the six counties sampled are 10.42 μg/l in Genesee County, 12.21 μg/l in Huron County, 19.26 in Lapeer County, 9.97 μg/l in Sanilac County, 6.66 μg/l in Shiawassee County, and 8.08 μg/l in Tuscola County.
Table 2: Arsenic exposure data for counties in SE michigan

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Figure 9: Exposure data for counties in Southeast Michigan. Source: Meliker et al., 2007

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According to these data, only three counties are below the EPA MCL of 10 μg/l (including Sanilac County, although the county is below by only 0.03 μg/l). In Shiawassee and Tuscola Counties, 100% of the population gets their drinking water from groundwater. These data show that residents in SE Michigan are overexposed to arsenic in drinking water. The data also show that residents in Shiawassee and Tuscola Counties only have the option of getting their drinking water at home from groundwater, which increases the likelihood of arsenic exposure from that source.

Based on the groundwater arsenic concentration data in [Table 2] and [Figure 9] from the same study, the study suggests that moderately elevated arsenic concentrations are associated with mortality from the previously mentioned diseases. Further epidemiologic studies are necessary to further increase the relationship between arsenic and mortality from the three diseases. [Figure 9] shows the population-weighted mean arsenic concentration in μg/l in six counties in SE Michigan.

[Table 3] displays the SMRs from 1979 to 1997 for the following counties in SE Michigan: Genesee, Huron, Lapeer, Sanilac, Shiawassee, and Tuscola. For males, there were 3493 observed deaths due to cerebrovascular diseases, with a 1.19 SMR and a 99% confidence interval (CI) of 1.14–1.25. For females, there were 5010 observed deaths due to cerebrovascular diseases, with a 1.19 SMR and a 99% CI of 1.15–1.23. For diabetes mellitus, there were 1249 observed deaths for males, with a 1.28 SMR and a 99% CI of 1.18–1.37. For females, there were 1612 observed deaths from diabetes mellitus, with a 1.27 SMR and a 99% CI of 1.19–1.35. Finally, for kidney diseases, there were 614 observed deaths in males, with a 1.28 SMR and a 99% CI of 1.15–1.42. For females, there were 679 observed deaths from kidney diseases, with a 1.38 SMR and a 99% CI of 1.25–1.52. [Table 3] shows the SMRs from 1979 to 1997 for the following counties in SE Michigan: Genesee, Huron, Lapeer, Sanilac, Shiawassee, and Tuscola.
Table 3: Standardized mortality ratios in six counties of Southeast Michigan study area, 1979–1997

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Previous studies have indicated that arsenic has been shown to be associated with increased rates of cerebrovascular diseases, diabetes mellitus, and kidney diseases.[36] [Figure 10] displays the proportion variance that is attributed to the different sources of inorganic arsenic intake in SE Michigan. The data from this study aimed to characterize the influence of arsenic concentration in water, consumption of water, exposure from arsenic in water at work, consumption of foods high in inorganic arsenic, and inhalation of arsenic from smoking cigarettes.[6] 1.3% of the sampled population ingested water contaminated with inorganic arsenic at places other than home or work, 1.3% from smoking cigarettes, 55.1% from water at home, 37.3% from food intake, and 5% from water at work. These data show that most residents of SE Michigan are exposed to inorganic arsenic in water at home.
Figure 10: Different sources of inorganic arsenic intake in Southeast Michigan. Source: Meliker et al., 2006

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[Figure 11] displays the factors that contribute to inorganic arsenic intake from water at home in SE Michigan. 88.6% of the sampled population consumed inorganic arsenic in drinking water, 7.4% consumed inorganic arsenic from beverages made with water, 3.8% ingested inorganic arsenic by consuming plain water, and 0.2% ingested inorganic arsenic from water used for cooking foods. These data also show that inorganic arsenic contamination in drinking water is a serious issue in SE Michigan.
Figure 11: Factors that contribute to inorganic arsenic intake from water at home in Southeast Michigan. Source: Meliker et al., 2006

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The results of this data analysis show a concerning problem with arsenic contamination in drinking water and disease risk in SE Michigan. The increased mortality from cerebrovascular diseases, diabetes mellitus, and kidney diseases and the relationship to arsenic exposure show that this is a serious public health concern in the area. This data analysis helped identify and confirm the prevalence of health issues related to arsenic exposure and the sources of arsenic exposure in the population.

Following the identification and confirmation of these problems, arsenic exposure mitigation in SE Michigan can be improved by creating and implementing solutions. The solution to the problems identified is for the state of Michigan to employ best available technology (BAT) to reduce arsenic concentrations in groundwater and well water. Examples of BAT identified by the EPA in the final arsenic rule include activated alumina, coagulation/filtration, ion exchange, lime softening, reverse osmosis, electrodialysis, and oxidation/filtration.[42] [Figure 12] illustrates the maximum removal capacities of the previously mentioned arsenic mitigation BAT.
Figure 12: Best available technologies identified by the Environmental Protection Agency in the final arsenic rule and maximum percentage of arsenic removal[42]

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In addition to the BAT, community awareness through the use of a public health system is needed to educate the population of SE Michigan on the hazards of arsenic exposure. This will help teach residents about where exposure to arsenic comes from, how to have well water tested for arsenic, and how to determine the water sample results.[43] A public health system awareness program through the MDCH could also inform residents about alternative options to reduce arsenic exposure in drinking water.


  Discussion Top


Unidentified problems

Unidentified problems relate to arsenic mobilization in SE Michigan. More research needs to be done to fully understand arsenic mobilization for this area. Arsenic levels have the potential to escalate if mobilization is not fully understood and anthropogenic activities escalate the issue. Another unidentified problem may be resources to implement large policy changes in the state of Michigan; funding could be a hurdle that would allow this issue to be ongoing. Another problem may be effectively targeting those of low socioeconomic status who are at risk for arsenic contamination. There need to be resources allocated to this. These issues need further exploration and study to be fully understood and therefore mitigated or controlled.

Recommendations

There are a number of ways in which to identify, mitigate, and control arsenic in SE Michigan. First, it is recommended that Michigan adopt a stringent policy to reduce public risk. New Jersey's Safe Drinking Water Act was updated by adopting a more stringent standard of 5 μg/l, which is the most protective in the United States. Michigan should also adopt a more stringent standard due to the arsenic concentrations seen in SE Michigan. Even small amounts of arsenic can have serious health implications.[44] Michigan can also learn from other New Jersey legislation that is in place. It is also recommended that Michigan adopt an act similar to the New Jersey Private Well Testing Act (PWTA) that requires untreated well water for arsenic during real estate transactions.

The PWTA has significantly increased arsenic testing rates in an area where many wells contain arsenic above 5 μg/l, which is New Jersey's drinking water standard. This practice could do the same for counties in SE Michigan. The PWTA also helped close socioeconomic gaps in testing for new homeowners because it reaches higher proportions of families with children. Residents purchasing homes now are typically younger and disproportionally more likely to have children in the household (60% vs. 32%). This is a priority group due to the vulnerability to effects of arsenic. The same would hold true if a similar act was adopted in Michigan.

Policy-level intervention is an important component of any strategy to eliminate exposure to arsenic from private well drinking water.[44] New Jersey's legislation has resulted in more at-risk households being identified and treated for arsenic and ensures that moving forward young households will be aware of drinking water quality and that socioeconomically disadvantaged households will not fall more behind in testing behavior. These are significant effects that should lead SE Michigan to consider similar private well testing regulations, especially in areas where a large number of residents drink from groundwater but are unaware of common risks faced such as naturally occurring arsenic contamination.[44]

Owners need to be aware, willing, and capable of managing proactive actions of well water testing and treatment on their own. The public needs to be provided with support for private well testing. Public health efforts are needed in SE Michigan to place emphasis on behaviors that protect health, such as reducing exposure to arsenic through avoidance or water treatment. With treatment in place, the public needs to be aware that regular maintenance and monitoring are of the greatest importance. When arsenic screening is increased in SE Michigan, resources must then be shifted to educate and support these households that are facing arsenic problems.[44] Education and community engagement are paramount to ensure a successful intervention. Those in the affected communities need to understand the risks of arsenic exposure and the sources of this contaminant.[1]

In regard to treatment and mitigation, there are a number of water treatment systems that remove arsenic and can either be configured to treat all water in the home or a single tap for drinking and cooking. Point-of-entry (POE) treatment is whole house water treatment whereas POU treatment is for a single faucet treatment. Technologies include adsorption processes such as granular iron, activated alumina, and titanium-based media; anion exchange resins; hybrid media that contain iron impregnated anion resin; and membrane processes such as reverse osmosis. For those facing arsenic issues in SE Michigan, evidence shows that POE arsenic water treatment systems are more effective in reducing arsenic exposure from well water versus POU treatment.[45]

Smaller systems in the SE Michigan area may also use bottled water to avoid arsenic contaminated water if there is an enforceable compliance agreement. Another solution is to provide hook-ups to municipal water when private well waters are tainted. The state may also help build new municipal water supply systems when there is no other reasonable alternative available.[46]

Well-drilling practices can be adopted in SE Michigan to address geology and how it impacts arsenic mobilization in drinking water. It is believed that recharging water is a source of arsenic in deep aquifers or it facilitates arsenic mobilization in SE Michigan. Arsenic concentrations are associated with the proximity of screening depth to an upper confining unit in glacial unconsolidated wells. This should bring forth policies as domestic bedrock wells are usually cased just a few meters below bedrock. This well-construction practice consequently draws water from a region of the aquifer likely most affected by arsenic mobilization. In response, Huron County, Michigan, now requires that well drillers case wells deeper into the bedrock, about 10–13 m below the bedrock-unconsolidated interface. This effort decreased arsenic concentrations after the change was adopted.[22] All counties in SE Michigan should adopt these well-drilling practices to provide safer water to the population inhabiting the region.

Healthy People 2020

Healthy People 2020 delivers science-based, 10-year national objectives aimed to improve health of Americans. Healthy People 2020 is utilized for strategic management by the federal government, states, communities, and numerous public and private-sector partners. It is a comprehensive set of objectives and targets that can be used to measure progress for health issues in specific populations and serves as a tool for prevention and wellness activities across numerous sectors and within the government and a model for measurement at both state and local levels. The vision is a society where all individuals live long, healthy lives.

There are 42 topic areas that highlight specific issues and populations.[47] The research presented meets criteria for a number of topic areas, namely public health infrastructure, cancer, educational and community-based programs, and environmental health. The goal of public health infrastructure is to make sure that federal, state, tribal, and local health agencies have the necessary infrastructure to effectively provide public health services. A recommendation to address arsenic exposure is to shift state resources to educate and support households with arsenic problems; therefore, this area is addressed by the presented research.

Another Healthy People 2020 topic area addressed is cancer.[48] The goal of this area is to reduce new cancer cases as well as the associated illness, disability, and death. Since arsenic is a known carcinogen and is associated with various types of cancer, mitigating and controlling arsenic as suggested would decrease cancer prevalence.

Educational and community-based programs, another area, are also touched on. The aim of this area is to increase the quality, availability, and effectiveness of educational and community-based programs aimed to prevent disease and injury, improve health, and improve quality of life. This area is met because education is a recommendation of the research; educating the public on arsenic can improve health when individuals know the risks and how to avoid said risks. The last area addressed is environmental health; the goal of this area is to promote health through a healthy environment. A large goal of the conducted research is to create a healthy environment through improving water quality using systems to remove arsenic and other controls to provide potable water to individuals living in SE Michigan.[48],[49]


  Conclusion Top


It has been shown that arsenic, even at low levels, has harmful effects to human health. The results of the presented data analysis showed a concerning problem regarding arsenic contamination in drinking water and disease risk in SE Michigan. Given that groundwater levels of arsenic in SE Michigan present a problem to human health, this must be addressed through careful mitigation and control. Some controls discussed include legislative action, systems for removing arsenic from water, adopting improved well-drilling practices, education, using bottled water, and more. Implementing discussed controls would increase the health and quality of life for those living in the affected areas. It is paramount that measures to be taken to address the arsenic problem in SE Michigan.[49]

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]


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