For the sake of understanding the basic terrain of the really big sustainability problems, I think that it makes sense to lump together all of the pollution outside of greenhouse gases, so that the really big problems are: biodiversity and ecosystem loss, global climate change, and ‘other’ pollution. This is certainly a vast oversimplification, but a useful one. I say this because biodiversity loss and climate change are ‘existential’ threats, meaning that if we don’t get these problems under control, we threaten the very future of humanity on the planet. In comparison, most of the other sorts of pollution that we create and are exposed to aren’t a threat to humanity as a whole, even though they cause massive health problems, increased mortality and other problems to those who are most exposed. Every major pollution pathway ought to be improved to reduce the damage to human health and to the living environment, but any one of these problems isn’t as dire as those of biodiversity loss and climate change.
A massive amount of the pollution that we produce is the byproducts of industrial processes and energy production. We want to build and drive cars, construct and heat homes, make medicines, kill weeds, and so on. Unfortunately all of this activity can produce substances that are toxic to human health, causing everything from lung disease to cancer, neurological problems to heart attacks. Many of these pollutants can be and often are cleaned up so that people are not exposed to them, but others are released into the air, water and earth.
Much of air pollution comes from burning, fossil fuels and wood for their energy, and the cooking involved in industrial processes to separate or refine the products that we need. The greatest threats from air pollution appear when people breathe this contaminated air. Being in the proximity of factories, or in the middle of cities that have smog problems, or poorly vented indoor cooking fires in developing countries, all contribute to increased mortality. Recent estimates of the effect of air pollution show that around 9 million extra deaths occur every year due to air pollution, mostly in the developing world. And for each death, there are many more who experience other serious negative health outcomes. Cutting the use of fossil fuels, particularly coal, would make enormous strides for human health as well as reducing the release of greenhouse gases.
Water pollution is often caused by the dumping of wastes into waterways. Water is a great means of transporting wastes, whether they be from factories, or mines, or even human sewage. The problem comes when these wastes aren’t remediated, neutralizing and removing the toxic parts before letting that water enter rivers, lakes and the oceans. Other wastes, known as non-point sources, fall into waterways after being distributed over a large area of land. Rain carries fertilizers and pesticides from farm fields, or oil and other chemicals from roadways, and puts those materials into streams and rivers. Slowing the movement of water over land, having healthy wetlands and vegetation along shores, all help to keep wastes from entering the water. Water pollution causes massive problems to human health, including the spread of disease from untreated sewage, or illness of all kinds from toxic chemicals that may get into the water we drink and use.
Finally there is the pollution of solid wastes, also known as garbage. It turns out that from a sustainability standpoint, non-toxic garbage isn’t a grave concern. We are in no danger of running out of places to dig big holes in the ground where we can stack up and bury our discarded stuff. Throwing away so much material may be wasteful, which carries a significant impact in itself, but the disposal doesn’t pose such large risks. The problems of physical wastes more often come when toxic materials leach into the surrounding soil and groundwater, or otherwise escape from a landfill. There are some particular problems that come from wastes like plastics, which are now accumulating but not breaking down out in the oceans, but these problems make for more localized threats to wildlife. There is much to be done to divert wastes from landfills, composting all the organic and food wastes, recycling more of the plastics and metals, and so on, but garbage is relatively far down the list as a sustainability concern.
Mostly I wanted to include this short essay to mention all of the wastes that we produce, even though this site is mostly to focus on addressing biodiversity loss and climate change. Very early in any discussion of environmentally sound behavior the topics of these sorts of pollution are going to come up. Often the same solutions can address many problems at once. For instance, increasing the efficiency of our energy and resource use means less greenhouse gas emissions so reducing global warming, less disturbance of ecosystems, and less production of other forms of pollution that have negative impacts on health.