In Utero and Childhood Exposure to Arsenic in Water and Lifelong Lung Disease

 

An estimated 20 million people in the US are exposed to levels of arsenic in their drinking water near or above the current regulatory standard. The developing lung may be particularly susceptible to environmental toxicants including arsenic. Previous studies from northern Chile suggest that people exposed to arsenic in water as young children or in utero have relative risks of lung cancer that are 3-4 times higher than those exposed as adults. Arsenic in water has also been linked to very high risks of non-malignant lung disease. However, these studies have not assessed the possible long-lasting or permanent effects of exposure during the critical periods of lung development. We propose a cross-sectional study of pulmonary function (measured by spirometry) and respiratory health in subjects from northern Chile who were exposed to high arsenic levels as young children or in utero and who are now adults. We will recruit 300 lifelong residents of the city of Antofagasta which had very high arsenic concentrations in municipal water supplies from 1958 to 1970. Measures of pulmonary function and prevalence of respiratory symptoms in these subjects will be compared to 300 age and gender-matched lifelong residents of Arica, a sociodemographically similar neighboring city with no history of high arsenic levels. All subjects will be randomly selected from the Chile electoral registry which contains 94% of the Chilean population. Urine samples will be collected for future biomarker studies of susceptibility and early effects. The advantage of doing this study in northern Chile is that this area is incredibly dry and almost everyone lives in one the few large cities and obtains water from one of a few large municipal water supplies. Because we have arsenic records for all these sources for the last 50 years, information on lifetime exposure can be much more accurate than anywhere else in the world. Also, a distinct period of high exposure occurring in Antofagasta about 40 years ago, with low exposure before and after, has created a large population (about 300,000) who were highly exposed in utero or as young children but not as adults. Studying health effects in these people now will allow us to investigate the long-term impacts of their early life exposure. A scenario like this, with its distinct period of high exposure, large population, high exposure in early life but not in adulthood, and accurate data on past exposure, is without precedent in environmental epidemiology.

 

The scientific importance of this project lies in the fact that little information is available in humans on the lifelong effects of environmental exposures that occur during critical periods of lung development. The public health importance lies in the need to incorporate information on early life exposure effects into environmental regulation, and in helping to assess whether more rigorous public health measures are needed to identify and prevent toxic exposures in children and pregnant women.

ARSENIC HEALTH EFFECTS RESEARCH PROGRAM

PROJECTS

Berkeley

University of California

Early life arsenic exposure and adult mortality in Region II, Chile

 

Millions of people in the US and worldwide are exposed to high concentrations of arsenic in their drinking water, and the estimated risks of cancer, cardiovascular disease, and other adverse outcomes associated with these exposures is very high. From 1958 to 1970, over 125,000 people in the city of Antofagasta in Region II of Chile experienced a sudden and unusual period of high drinking water arsenic concentrations. This exposure period was highly distinct, with low exposure before the highly contaminated drinking water sources were first used in 1958, and a sudden drop in water arsenic concentrations (from around 870 g/L to eventually 10 g/L) when an arsenic removal plant was installed in 1971. As far as we know, a scenario like this, in such a large and uniformly exposed population, has never been reported for any environmental contaminant.

 

Our investigation of this unique population has already been highly productive. For example, we identified major increases in mortality in Antofagasta among people who were young children or in utero during the high exposure period. These increases were found for bladder cancer (standardized mortality ratio [SMR]=21.3; 95% confidence interval [CI], 11.6 to 35.7), laryngeal cancer (SMR=10.5; 95% CI, 3.4 to 24.6), lung cancer (SMR=6.8; 95% CI, 5.4 to 8.4), kidney cancer (SMR=3.4; 95% CI, 1.7 to 6.2) and liver cancer (SMR=3.1; 95% CI, 1.8 to 4.9). Non-cancer deaths were increased from bronchiectasis (SMR=25.1; 95% CI, 13.4 to 42.9), acute myocardial infarction (SMR=2.4; 95% CI, 1.9 to 3.0) and chronic renal disease (SMR=2.3; 95% CI, 1.6 to 3.3).  Increases were greatest for those born during the high exposure period (with likely in utero exposure) for bladder cancer (SMR=55.9; 95%CI, 25.5 to 106) and bronchiectasis (SMR=46.2; 95%CI, 21.1 to 87.7). This was the first human study to link early life exposure to a common drinking water contaminant to high risks of cancer and non-cancer outcomes in adults. Because of the timing of the high exposure period (1958-1970), our previous studies could only assess the long-term effects of early life exposure in relatively young adults (i.e., those in their 30s and 40s). In this proposal, we seek to extend our investigation to cover ten additional years of mortality data, from 2001-2010. This will allow us to evaluate whether the effects of early life exposure we identified in young adults continue into older age groups. This is important because the baseline risks for most chronic diseases are higher in these older age groups. Because of these higher baseline risks, increases in relative risk due to arsenic in these older groups would cause larger numbers of arsenic-related deaths, and therefore larger increases in the overall burden of disease in exposed populations.

 

Currently, many people in the US use private wells with high concentrations of arsenic, including some as high or higher than they were in Antofagasta. Region II of Chile provides the best population in the world to assess the effects of early life arsenic exposure. The reasons include the fact that this is the driest inhabited place on earth, with only one water source for each town and city and accurate records of arsenic concentrations for the last 50 years or more. The limited number of water sources and availability of good records means that arsenic exposure from the distant past can be assessed with greater accuracy than can be done anywhere else in the world. This accurate data on exposure substantially reduces the exposure assessment problems (i.e., ecologic fallacy) commonly seen in many ecologic studies. Another advantage is that the number of people who were highly exposed in Antofagasta is more than ten times greater than in any other published arsenic study in the world. In this situation, the ecologic study design is ideal, since it allows us to study a variety of different causes of death, in a very large exposed population, with good data on past exposure, good statistical power, and a low probability of major confounding.

This mortality study is probably the only opportunity available to see if the already identified major effects of early life exposure to arsenic on multiple causes of death in young adults continues into older age groups. This would have several important public health implications. For example, health care providers in the US and worldwide would need to be more alert to arsenic health effects and exposure, especially in pregnant women, infants, and young children, and should ask all patients from rural areas if they have private wells, and if they have been tested for arsenic. In addition, the current drinking water standard of 10 g/L might need further examination, since the risk estimates on which this standard is based did not consider the risks associated with early life exposure.

 

Toxic Substances in the Environment: Arsenic Biomarkers Epidemiology

 

Arsenic is ranked number one on the Superfund Priority List of Hazardous Substances. Our findings indicate that early life (i.e. in utero and early childhood) exposure to arsenic causes increases in adult mortality greater than that from any other known toxic exposure. During the last five years, our arsenic research program has discovered that early life exposure to arsenic results in major mortality increases among young adults aged 30-49 from lung cancer and bronchiectasis , myocardial infarction, and kidney cancer. More recently we found increased young adult deaths from bladder cancer (20-fold increased mortality), laryngeal cancer (10-fold increased mortality), and chronic renal failure (2.7-fold increased mortality) (in preparation for publication). Our recent work has also identified even more causes of death related to arsenic, including cancers of the thyroid, penis and cervix. Among non-cancer outcomes, pulmonary tuberculosis had a clear latency pattern of increased mortality following exposure to arsenic, and we have also found evidence of increased mortality from respiratory and urinary tract infections (in preparation for publication).

 

In light of these surprising new findings, the study focuses on the effects of early life exposure to arsenic with studies in targeted Chile and Bangladesh populations, both having unique features related to arsenic exposure in early life which make them ideal study populations. Our findings of multiple cancer and non-cancer outcomes call for identification of mechanisms of action consistent with these effects. We have found in two independent populations that urinary protein levels of an important tumor suppressor gene, human beta defensin 1 (HBD1), are markedly reduced in men exposed to high versus low levels of arsenic. Using new, enhanced technology, two-dimensional differential in-gel electrophoresis (2D-DIGE), we will now be able to identify other differentially expressed proteins in urine from arsenic-exposed populations. Moreover, we found that arsenic treatment of kidney and bladder cells led to a persistent down-regulation of HBD1 gene expression. One possible mode of action is that arsenic exposure results in epigenetic alterations in genes such as HBD1 that can lead to their suppression, with global changes affecting multiple organs and multiple cell types, especially during exposure in early life.

 

This study is an integrated research strategy assessing multiple outcomes in population studies, focusing on effects from early life exposure and pursuing evidence concerning mechanisms of action of arsenic in the same study populations. The studies in Bangladesh and Chile contain the four following aims:

 

Aim 1: Investigate preliminary new findings of increased mortality due to pulmonary tuberculosis, chronic renal failure, and increased mortality from cancers of the larynx, penis, cervix and thyroid gland, including assessment of the consequences of early life exposure to arsenic in Chile.

 

Aim 2: (a) Investigate the effects of arsenic in a unique cohort of Bangladesh children who were exposed in utero and in early childhood, assessing the incidence of chronic respiratory disease, including measuring lung function, upper respiratory tract infections and pneumonia, measuring blood pressure, and measuring β2-microglobulin in serum, a marker of reduced kidney glomerular filtration rate; (b) In this same cohort, collect urine samples and buccal cells to identify epigenetic alterations and proteomic biomarkers of arsenic exposure, susceptibility, and disease.

 

Aim 3: Assess the effects of early life arsenic exposure on lung function and respiratory symptoms in northern Chile by (a) administering high resolution CTs and questionnaires on past lung infections; (b) collecting buccal and urine samples for studies of genetic, epigenetic and proteomic biomarkers of exposure, susceptibility, or disease that might be found many years after high exposure;. (c) collecting saliva for high-throughput genotyping studies to determine the effects of genetic variation in N6AMT1, MYST1, FEN1 and other genes identified in Project 2 on lung function in individuals with previous exposure to arsenic.

 

Aim 4: Conduct in vitro studies to determine the mechanism and downstream effects involved in the persistent down-regulation of HBD1 gene expression by the toxic arsenic metabolite, MMA3. We will perform epigenetic studies using kidney and other target organ cell lines, including knocking down HBD1 gene expression to determine the genes that are affected by HBD1 down-regulation.

2470 Telegraph Avenue, Suite 301, Berkeley, CA 94704 Tel: (510) 990-8354 Email: asrg@berkeley.edu