Welcome back, in this session, let's talk about Environmental and Ecosystem Health. Agriculture began around 10,000 years ago, and for almost half that time, farmers have been battling pests with natural compounds such as sulfur and pyrethrum, which was derived from dried flowers, and here's an image of farmers harvesting their crops. They used a variety of naturally derived compounds such as copper sulfate and lead and organic nicotine and pyrethrins, and these were used since the 1940s. But during World War II, synthetic pesticides were developed and these compounds could be very, very toxic. Now the challenge with agriculture is you want to be able to grow enough food to feed millions of people. And pests and disease caused significant losses, between 20 and 40% of global crop yields are reduced each year to the damage caused by disease and pests. As I mentioned in the previous session, Rachel Carson published a seminal book, "Silent Spring", highlighting the dangers of pesticides to human, animal, and environmental health. Insecticides had a dramatic effect on human, animal, and environmental health. Insecticides were designed to kill insects, but they were also very dangerous to other living beings. The effect on bird's eggs were dramatic and you can see these eggs showed that they were unable to maintain their shape as the parent bird laid on them to incubate them. Acute exposures to people resulted in abdominal pain, nausea, vomiting, dizziness, and headaches. Insecticides had deleterious effects on health from acute exposure. Long-term exposures over months or years could cause cancer, birth defects, neurodevelopment problems, and even fetal death. Neonicotinoids are a class of pesticides that are chemically similar to nicotine in cigarettes. The problem with these pesticides is they not only killed pests, but they killed off important insects such as pollinators like bees, contributing to colony collapse disorder where bee populations plummeted. The public demanded clean air, clean water, and a clean environment and in response, the government established the Environmental Protection Agency in 1970. Its mission was to develop policies to protect human health and the environment using the best available science. In May 2016, the report titled "Healthy Environments, Healthy People" stated that an estimated 12.6 million deaths globally were attributed to environmental causes. The air, the food, the water, the ecosystems that are supposed to sustain us, if they're contaminated, they can cause an estimated 23% of all deaths worldwide. 20% of all cancers worldwide are estimated to be due to environmental factors. Air pollution is the single largest environmental risk to health causing approximately 7 million people to die each year because of poor air quality. Environmental pollutants can impact our health whether we inhale them such as particulate matter or coal dust or ingest them inadvertently through pesticides or lead or hearing the noise that's produced by transportation or other sources. All of them can adversely affect our health. Let's compare environments versus ecosystems because they're often confused or used interchangeably. The environment includes the non-living or the abiotic factors and the living, the biotic factors in a defined geographic area. In contrast, the ecosystem refers to the interactions between the animals, plants, and microorganisms or all of the biotic factors in a specific defined area. So let's discuss environments first. The World Health Organization issued a report, Healthy People 2020 and it considered environmental health as preventing or controlling disease, injury, disability related to the interactions between people and their environments. This report, Healthy People 2020, had six different themes focusing on air quality, water quality, the global environment, infrastructure, and surveillance. Let's define environmental health. The National Environmental Health Association or NEHA defines environmental health as the science and practice of preventing human injury and illness and promoting well-being by identifying and evaluating environmental sources and hazardous agents, and by limiting exposures to hazardous agents in air, water, soil, and other environmental media that might adversely affect human health. We need to do environmental monitoring and that usually focuses on measuring the chemicals, pollutants, toxins, or waste in our soils, airs, and waters. Here's an image of a monitoring system. What exactly does soil quality, air quality, or water quality mean? Well, the Merriam-Webster dictionary defines quality as a degree of excellence. So we want excellent air, water, and soil. In the case of environmental quality, then we can extrapolate it to define it as a degree of purity, free from chemicals, pollutants, and wastes. So monitoring can be both outdoors and indoors. But in this course, we're going to focus on outdoor exposures rather than indoor environmental exposures. So you can do physical and chemical tests on your water. Physical test will include the color, the odor, how cloudy the water is, the temperature of the water, and how much stuff is floating in it, like vegetation. Chemical tests will look at the pH or the acidity of the water, the dissolved oxygen level, or the phosphate levels, and nitrate levels. Heat takes oxygen out of water and that's very bad for the fish and for the other organisms living in the water. Because if they don't have oxygen, then they could die. You can do a biological assessment of streams. So rather than looking at the chemicals or the physical qualities of water, you can look at the biological aspects of the water. And you do that by using macro invertebrates such as insects, snails, and crayfish. So for example, some organisms are sensitive to pollutants or toxins and they will die readily in response to the exposure of these chemicals. Stoneflies pictured on the top are particularly sensitive to contaminants and they will die if exposed to minimal levels. Less sensitive organisms such as the scud pictured there can tolerate some degree of contamination. And then you have tolerant organisms such as these orb snails that can live in polluted waters. So if you have a waterway that just has orb snails, you can pretty well conclude that that waterway is pretty polluted. You can calculate your biological water quality based on the ratios of the sensitivities of these different organisms. You can also look at air quality standards. The Environmental Protection Agency sets national standards for air quality to six common pollutants. They include ozone, particulate matter or little bits of particles that you can inhale deep into your lungs, carbon monoxide, nitrogen dioxide, sulfur dioxide, and lead. You can take these different compounds and develop an air quality index. So you determine the risk level for each of these six pollutants during a specified period of time. So you can create an air quality index then for each pollutant. You can look at the global air quality for one pollutant such as particulate matter that you can inhale deeply into your lungs and can cause serious damage. So in 2016, you can look at the global air quality, and right away, you can see that the air quality in Africa and South Asia can be quite dangerous with very high levels of particulate matter. Soil quality is broadly defined by how well it functions to sustain agriculture and produce food for people and animals. Soil quality is measured by physical, chemical, and biological indicators such as soil structure, depth, and water holding capacity, the pH or acidity level of the soil. The amount of nitrogen and phosphorus and potassium, and the biological aspects of the soil including the microbial biomass, the microorganisms, the organic matter that's in the soil that makes it rich and able to grow crops. Without government regulations and oversight, corporations and other actors can contaminate the soil at will. In 1980, the US government established the Superfund sites highlighting different areas around the country that have contaminated waste and toxins that were dumped in specific areas. As of 2016, there were over 1,300 of these Superfund sites. Many of them concentrated in the northeastern part of the United States. One of the challenges with environmental health is establishing causation from exposure to pollutants and other contaminants. You have to establish a dose-response relationship between the exposure and the health outcome. People often move from place to place which makes attribution difficult. And animals can be an important sentinel for environmental contamination, but they're usually ignored. Let's talk now about ecosystems. The US Fish and Wildlife Service defines a healthy ecosystem as consisting of native plant and animal populations interacting in balance with each other and with non-living things such as the soil and the water. And these ecosystems have definite geographical boundaries. Components of a healthy ecosystem include living organisms, an energy source, typically sunlight, non-living components, of course, the soil, air, and water, dead organisms, and natural boundaries. You can readily differentiate between a healthy and a sick ecosystem. I think we can all agree that this picture is a healthy ecosystem while this picture is a sick ecosystem. Large animal die-offs are another important sign of a sick ecosystem as pictured here, large scale die-offs of fish or of sea mammals. So the questions for this section include, What is the difference between a healthy environment and a healthy ecosystem? Who monitors the water, air, and soil quality where you live? Would you consider the environment in which you live to be healthy? And if not, what do you think would need to be done to make it healthy? How did the environmental movement begin? What are the pros and cons of pesticides? What are some of the health consequences of pesticides? And finally, which environmental factor poses the greatest risk to health? And with that, I'd like to thank you for your time and attention.
