Distilling the truth about water
[ Winter 2013 ]
HSPH’s James Shine explains why access to safe water persists as a global health issue.
Water courses through every aspect of our lives, for good or ill. As senior lecturer on aquatic chemistry in the School’s Department of Environmental Health, James Shine has explored the role of clean, safe, and accessible water in human health, focusing on the effects of contaminants in rivers and lakes. According to Shine, the global water cycle is vast and mysterious—and as crucial to our survival on the planet as the global carbon cycle, the mechanism by which carbon circulates through the earth’s atmosphere and plays a role in global warming. Shine spoke recently with Harvard Public Health editor Madeline Drexler.
Q: How much water does an average American consume each day?
A: About 1,600 gallons. That figure surprises a lot of people. Most of us think about our direct-consumption use of water: How many times do I flush the toilet? How long is my shower? And those are obviously important for understanding how one person depletes local water resources. But if you start thinking larger, you’ll see that a drop of water that fell on a wheat field this afternoon is going to be part of my sandwich bread five months from now. If it’s a ham sandwich, a lot more water was used. It takes 52 gallons of water to make one glass of milk. It takes more than 600 gallons to make a quarter-pound hamburger. It takes 2,800 gallons to make a pair of jeans. Our daily lives carry a giant water footprint.
Q: Population and industrial production and per capita consumption keep going up. But the water supply is finite. Aren’t humans relying on basically the same amount of water that we were 10,000 years ago?
A: Yes—although, of course, it’s not the same water. About 97 percent of the water on our planet is in the oceans. Another 3 percent is in the polar ice caps. We humans use the very small fraction of fresh water that is accessible groundwater and surface water, such as lakes and rivers—all told, about 0.1 to 0.2 percent of water on the earth. That amount has been stable since the last ice age, and although water is constantly cycling in and out of the different pools, we are altering the quantity and quality of available fresh water.
“ It takes 52 gallons of water to make one glass of milk. It takes more than 600 gallons to make a quarterpound hamburger. Our daily lives carry a giant water footprint.”
Q: Will climate change alter the water cycle and therefore the amount of water that we can draw on?
A: That’s the question. There could be more rainfall, more flooding, as well as more drought, meaning there will be winners and losers. As ice melt and river runoff increase in the North Atlantic, that less dense fresh water might ride on top of the warmer Gulf Stream; the Gulf Stream, which crosses the Atlantic, would no longer bring heat to Europe. In that scenario, Europe’s climate might be more like northern Canada’s, which would be a big public health problem. In other areas, changes in water flow can have harmful effects on human health in many ways. Areas at higher latitudes that receive greater amounts of rain may have more floods, creating stagnant backwaters that make better habitats for the vectors of malaria and schistosomiasis and other waterborne diseases.
Q: How are we doing on the 2015 Millennium Development Goals (MDGs) that relate to water and sanitation?
A: On a global basis, the world has already met the MDG for safe water. China and India have made great strides in providing safe drinking water through direct piping of clean water or the use of deep wells; unfortunately, sub-Saharan Africa is not meeting its drinking water goal. As for sanitation, the problem is that, in the developing world, about 40 percent of people use open defecation or public latrines. In India, there are more cellphones than toilets. Worldwide, 2.5 billion people lack access to adequate sanitation and 1.8 million die annually because drinking water becomes contaminated. The sanitation goal clearly will not be met by 2015. The point is that we need to think of safe drinking water and sanitation together—as one problem. They shouldn’t be separate MDGs.
Q: You are a marine chemist by training. Was there an “Aha!” moment for you—a moment when you knew that you wanted to study water within the context of public health?
A: Yes, I even remember when and where it happened. After I was an undergraduate, I worked in an environmental chemistry lab, testing people’s drinking water and well water. My job was to determine if the results were above a certain threshold or below it: above or below the line. After a while, I wanted to know, well, where did that line come from? Who decided where the line was going to be drawn? Good science must always be connected to the real world and to real lives.