Earthrise is one of the best-known photographs of the 20th century. It was taken by Apollo 8 astronauts on Christmas Eve, 1968. It shows the incredible beauty of the Earth. At the same time, it hints at the planet’s fragility and smallness in the emptiness of space. Earth has provided us with everything we have. However, the Earth, and we as its inhabitants, are paying a steep price because of what we have done to it and what is likely to happen.

The first Earth Day was celebrated on April 22, 1970. That same year, Congress established the Environmental Protection Agency and passed the Clean Air Act. The EPA’s mission is “to protect human health and the environment.” The act required the EPA to identify the most dangerous and common air pollutants and establish air quality standards for each. These are known as National Ambient Air Quality Standards or NAAQS. They are designed to protect everyone. They emphasize those who are the most vulnerable to these pollutants, such as asthmatics, children and the elderly.

There are six of these criteria pollutants: lead, oxides of nitrogen, carbon monoxide, oxides of sulfur, ground-level ozone and particulate matter. The smallest particulates are the deadliest. They measure 2.5 millionths of a meter in diameter or less and are known as PM2.5. Typical hairs measure about 70 millionths of a meter in diameter. Ozone is formed from oxides of nitrogen in chemical reactions powered by sunlight, so emission data can’t be compiled.

Counties where there is a persistent failure to meet NAAQS standards are known as non-attainment areas. In 2012, Erie, Niagara, Orleans and Genesee counties failed to meet standards for one pollutant. Chautauqua County failed to meet two. Across the nation, 158 million Americans live in non-attainment areas.

The EPA monitors the amount of carbon monoxide, oxides of sulfur, ground-level ozone and PM2.5 at more than 1,000 sites. These data become the Air Quality Index. This index can be found at the EPA website known as Enviroflash, apps for smartphones and the Buffalo News weather forecast. The index ranges between 0 and 500, and is a predictor of how likely your air will cause a health problem, such as an asthma attack, in the relatively near future. An index of 50 or less indicates good air. Anything above 300 warns of an immediate serious health hazard. However, there is no completely safe level for any of these pollutants.

Numerous studies published by leading scientists, doctors and epidemiologists in top-tier medical journals have provided unequivocal evidence linking criteria pollutants to the top four causes of death in the United States. These are, in order, heart disease, cancers of all types, diseases of the lungs and respiratory system, and stroke.

The newest data from the Centers for Disease Control and Prevention attributed almost 1.5 million deaths to these diseases in 2008. Many of these deaths and associated serious and minor illnesses can be prevented by making our air cleaner and safer to breathe.

Pollution linked to illness

Investigators in Taiwan and Korea have linked small particles, carbon monoxide, oxides of nitrogen and oxides of sulfur with an increased risk for stroke. These studies were reinforced by results from the Women’s Health Initiative, which included research done at the University at Buffalo. They found a significant link between increases in small particles and heart attacks, strokes and the need for coronary artery bypass surgery.

Other studies using the Medicare database showed links between PM2.5 concentrations and hospitalization rates for heart failure, abnormal heart rhythms and cardiovascular disease. More recently, transient increases in the concentration of small particles that do not exceed the EPA criteria increase the risk of a stroke by about 10 percent. The list of other studies is very long.

As health care research has advanced, air pollution has been tied increasingly to the severity of disease, the numbers of patients affected and the number of diseases involved. Preliminary studies suggest that air pollution may increase the risk for developing Alzheimer’s disease and Type II diabetes.

Some bright spots on horizon

But there is good news amidst the bad. The Clean Air Act Acid Rain Program has led to dramatic reductions in the emissions of oxides of sulfur and nitrogen. As a result, we have healthier air to breathe, and lakes in New York and elsewhere are coming back to life. Small particle concentrations have fallen.

Buffalo is a big winner in this regard. In a study of 51 metropolitan areas between the years 1978 and 1982, the Erie County life expectancy was 73.5 years when the average PM2.5 concentration was 26.5 micrograms per cubic meter of air. By 1999 and 2000, life expectancy had risen by 3.4 years. A good deal of that increase was due to a reduction in the PM2.5 concentration of just over 50 percent.

An EPA report to Congress predicts that by 2020, the Clean Air Act will prevent 230,000 premature deaths and result in about 2.4 million fewer asthma attacks, 17 million fewer lost days at work, 200,000 fewer heart attacks and many other health benefits. Associated health care savings are expected to be around $2 trillion per year, at a cost to industry of around $65 billion – a 30 to 1 return. This is a win-win-win situation. Americans enjoy better health, we curb health care costs and reduced federal and state expenses provide debt relief.

Climate change is looming

There is a dark cloud on the horizon – global warming. As a result of expanding economies and the need for more energy, we inject trillions of tons of carbon dioxide into the air each year. From measurements of concentrations in air bubbles trapped in ancient ice, we know that atmospheric carbon dioxide levels are higher now than at any other time in the past 435,000 years. The concentration of other global warming gases such as methane and nitrous oxide are also rising.

Four independent studies conclude that current global temperatures have risen by about 1.4 degrees Fahrenheit compared to a 1950 to 1970 baseline. Multiple lines of evidence show that the rise in carbon dioxide and increasing temperatures are the result of human activity – mainly, burning fossil fuels such as coal, oil and natural gas.

We can see the health consequences of global warming in the form of heat-related deaths and illnesses, worsening epidemics of diseases such as West Nile encephalitis and dengue, or break-bone fever, malaria and others. Severe weather events, such as droughts and superstorm Sandy, are becoming more frequent, causing deaths, injuries and refugees. Rising ocean waters are likely to displace 8 million people by 2050 as low-lying deltas flood.

According to the World Bank, last summer’s droughts caused a 10 percent increase in world food prices in July 2012 alone. This will worsen childhood malnutrition that already nears 50 percent in many Third World nations, according to another World Bank report. Climate scientists tell us that unless we curtail greenhouse gas emissions very soon, global temperatures will reach what they call the tipping point – the point of no return.

New York can the lead way

The EPA has classified carbon dioxide as a pollutant and is taking steps to curtail its emissions. Courts have upheld these actions, declaring that “the agency was unambiguously correct” and “this is how science works.”

A recent report by Stanford University and Cornell University professors shows how New York can lead the way in combating climate change by using wind, water and solar energy to supply all of the energy used for virtually all purposes by 2030. Installing about 16,000 wind turbines, rooftop solar cells on homes, governmental and commercial buildings, and taking better advantage of geothermal, hydroelectric and tide energy could meet the demand. Energy efficiency would increase.

And once generators are in place, fuel prices would drop to zero along with the emission of the worst pollutants. Most of New York’s energy jobs are out-of-state, so their plan creates more in-state jobs than would be lost. They estimate that pollution reductions would save New Yorkers about 4,000 lives per year and $33 billion in morbidity-mortality costs.

In medical school, we grew bacteria in petri dishes. When there were only a few, they grew rapidly in the seemingly inexhaustible food supply. With time, food was depleted and metabolic wastes halted their growth. They died. We humans on Earth are a bit like the bacteria – the resources of the Earth once seemed infinite, but they are not. The Earthrise photograph puts this in perspective, and Earth Day should remind us of Earth’s bounty and peril. Our activities have placed us and our planet at risk. Unless we change our ways, our children and grandchildren will inherit a very different and much more hostile planet.

As a neurologist, I know how magnificent our brains are and what they can do. The question is whether we have the wisdom that matches our potential.

Alan H. Lockwood, M.D., F.A.A.N., is emeritus professor of neurology and nuclear medicine at the University at Buffalo and director and co-chairman of the Environment and Health Committee for Physicians for Social Responsibility.