It’s been said the profession that has done the most to advance human health and longevity is civil engineering, in consideration of the virtual elimination of typhus and other waterborne diseases in the U.S. via water purification/disinfection and wastewater treatment. Considering engineering in toto, this assertion is even more true today, with advanced water treatment practices and the diagnostic and surgical equipment and systems that are the products of the engineering profession.
When we consider advances in human health, we naturally think of state-of-the-art medical centers rather than what comes out of our taps and is discharged to our lakes and rivers, but potable water and treated wastewater are actually a first line of defense against disease.
CLEANING UP OUR WATER:
In the early 1900s, many in Michigan and the U.S. were still getting sick, and some were dying, from typhus and other waterborne diseases, and not just the poor. Wilbur Wright died from typhus; so did Genevieve Jones, who was called “America’s other Audubon.” When potable water filtration and disinfection became the norm, and when the deadly connection between untreated wastewater outlets and water intakes (and outhouses and drinking water wells in rural areas) was made, these waterborne scourges were practically eradicated. Unfortunately, too many places in the world haven’t yet adopted the water treatment practices that America implemented in the first half of the 20th century, and are still plagued by waterborne diseases. Addressing this problem with more medical clinics and drugs is akin to dealing with a leaky dike by supplying more buckets.
Today, from a human health standpoint, the focus is on pathogen elimination in the water that’s delivered to customers, including bacteria such as Salmonella typhi (typhoid fever), Vibrio cholera (cholera), and Yersinia enterocolitica (gastroenteritis). Viruses of concern include polioviruses, echovirus (meningitis), and Hepatitis A Virus. Protozoans of concern include Giardia lamblia and Cryptosporidium (gastroenteritis).
Most municipalities rely on chlorination to achieve the disinfection standard and to provide a residual amount of chlorine in the water transmission mains, but chlorine can cause taste and odor problems (when overdosed) and may produce trace quantities of toxic byproducts, like chloroform. Ultraviolet (UV) radiation, already well accepted for wastewater disinfection, is increasingly being considered for potable water disinfection.
The advantages of UV disinfection are no trace toxic residuals, no taste/odor problems, and no chemicals added to the water, but disadvantages are higher energy costs and the lack of a protective disinfecting residual in the water system. Studies indicate that UV disinfection can effectively destroy bacteria, viruses, and protozoa of concern, but different pathogen testing should be performed than for chlorination plants. Water plant laboratories normally test for total coliform as a surrogate for pathogens, but because coliforms are sensitive to UV light, microbial tests for UV disinfected water ought to include a Heterotrophic Plate Count (HPC) test, which may provide a better disinfection assessment than the UV-sensitive coliforms.
Another area of concern involves the presence of trace concentrations of pharmaceutical and personal care products, which have been shown to be ubiquitous in water sources and water delivered to customers. These compounds include antibiotics, antimicrobials, antidepressants, endocrine-disrupting chemicals (such as natural and synthetic estrogen), cosmetics/fragrances, and calcium-channel blockers. To keep this issue in context, there is no scientific evidence that shows an impact on human health at these trace levels – parts per billion or parts per trillion. These compounds are not currently regulated in America’s drinking water, but endocrine effects in fish have been observed at higher concentrations. Furthermore, one study has shown that food and beverage intake of these endocrine-disrupting chemicals is many times, and often many thousands of times, greater than the amounts ingested by drinking potable water.
When we talk about the environment, water quality, and human health, there is another factor to consider: is there such a thing as too clean?
IS TOO CLEAN A PROBLEM?
Scientists have been trying to figure out why immune system diseases have been dramatically increasing in the developed world in recent decades. One theory suggests that our environment has become so clean that humans aren’t exposed to microorganisms in the environment to the extent that they once were, and aren’t exposed to bacteria that help regulate the immune system, perhaps contributing to diseases (like asthma) in which the body’s immune system is weakened (In a Squeaky-Clean World, a Worm Might Help Fight Disease, Shirley S. Wang, Wall Street Journal). Our excessive hygienic practices may affect the body’s ability to fight infection when encountered (Bug Me: Our Bodies Need Microbes and Worms, Matt Ridley, Wall Street Journal). On balance, water purification, hygiene, and medicine have increased our longevity and health, but there may be some unintended consequences.
Water is the most precious natural resource on the planet, and making sure our water is clean is a critical human health priority.
Thomas M. Doran, PE, is an adjunct professor of civil engineering at Lawrence Technological University, a member of the ESD College of Fellows, and a former Principal at Hubbell, Roth & Clark, Inc.