Perhaps the world’s greatest environmental disaster and mass poisoning was an unintended consequence of a good intention. It occurred in Bangladesh, the most densely populated country in the world, with a population of approximately 160 million.
While initially part of Muslim Pakistan when Pakistan separated from India in 1947, Bangladesh became fully independent in 1971. Much of the country is highly rural with a rich network of rivers, canals, streams, lakes and irrigation ditches. Many Bangladeshis obtained their water from these surface or near-surface water sources. Unfortunately, these surface water sources were contaminated by various types of harmful bacteria, which caused rampant diarrheal illnesses in both the pediatric and adult populations. Thus, there were high mortality rates from dysentery, cholera and similar illnesses, with perhaps a quarter of a million deaths each year in this country.
In an effort to remedy this problem, the United Nations Children’s Fund (UNICEF) and other agencies decided to dig deep wells that would bypass the bacteria that live in shallower water, and thereby provide clean water both for drinking and for irrigation needs. The digging of these wells began in earnest around 1971, and has resulted in hundreds of thousands of such wells. While at first it was difficult to convince those living in villages to switch over to the clean well water, ultimately they were mostly successful; well water is now utilized as the source of water by almost 75 million Bangladeshis.
However, there was a twist. In 1993, testing showed that the geological base in Bangladesh is naturally contaminated with extraordinarily high levels of arsenic. As a consequence, most of these new wells have dramatically high levels of arsenic, among the highest in the world. While the U.S. Environmental Protection Agency considers a level of 10 micrograms/liter (mcg/l) to be the safe limit for arsenic, most of the Bangladeshi wells are over 100 mcg/l. Some are over 300 mcg/l.
In essence, the Bangladeshis using these deep wells experienced significant chronic arsenic poisoning, sometimes over decades. As you might imagine, years of drinking water naturally poisoned with arsenic had many health consequences. A large number of the Bangladeshis have developed arsenicosis, which constitutes a spectrum of symptoms that include characteristic skin lesions, kidney and heart problems, diabetes and pulmonary problems. These problems were recognized fairly quickly.
Because of cancer’s longer latency, the impact of arsenic exposure on cancer risk was not as quickly recognized. Significant arsenic exposure can cause high rates of skin cancer. These are mainly the nonmelanotic skin cancers—basal cell and squamous cell carcinomas. Arsenic can also lead to increased rates of certain internal cancers—lung, bladder, kidney, liver and prostate cancer.
It is estimated that arsenic exposure has doubled the cancer rates in Bangladesh at this time. The main cancers that have been affected are lung, liver and bladder cancers. In truth, skin cancers are most increased but since these are nonmelanotic skin cancers, they do not tend to be fatal. Some studies have further suggested that in utero exposure to arsenic groundwater has also contributed to a future risk of adult cancers. Of note, it is believed that, because of the long latency of cancer, we have not yet observed the full effects of arsenic exposure in this population on cancer outcomes.
What can be done to improve the ongoing situation? One intervention has been to try to restore the water drinking habits of the population back to the surface water. This has been difficult because the villagers now like the taste of the arsenic-contaminated groundwater. Another problem with this approach is that it brings them back to the original issue that started the mess—the bacterial infections borne by the shallow water. Another possible solution has been to develop methods for reducing arsenic levels in individuals who have accumulated unusually large burdens of arsenic. There are methods for doing this, but it is costly and difficult to implement. Folic acid supplementation may reduce the arsenic burden in the body, so that may prove to be a useful intervention.
Ultimately, this public-health catastrophe is a prime example of how well-intentioned actions can have significant deleterious unintended consequences. UNICEF dug deep wells to help Bangladeshis avoid contaminated surface water and prevent diarrheal illnesses. Ultimately, though, they exposed Bangladeshis to years and years of slow arsenic poisoning in the process.
Alfred I. Neugut, MD, PhD, is a medical oncologist and cancer epidemiologist at Columbia University Irving Medical Center/New York Presbyterian and Mailman School of Public Health in New York.
This article is for educational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment, and does not constitute medical or other professional advice. Always seek the advice of your qualified health provider with any questions you may have regarding a medical condition or treatment.
