In recent years, many people, including this writer, have written many articles about many types of environmental problems in our water, air, land, food, workplaces and indoor environments.  However, we can be thankful that major progress has been made on many environmental health fronts including outdoor air quality, water quality and lead abatement.

The outdoor air quality in many US cities and towns has improved significantly since the 1960’s, even though the US population has grown to over 300 million.  A number of factors have contributed to cleaner US outdoor air including: 1)  The US Clean Air Acts of 1963, 1970 and later have reduced industrial and power plant air pollution,  2) Emission standards have been enacted for cars and other vehicles.   Carbon monoxide and hydrocarbon pollution from car exhaust has fallen by more than 90% since the 1960’s, 3) Lead has been removed from gasoline, 4) Natural gas has replaced dirtier burning coal for home heating in many parts of the country, 5) Emissions have been reduced from coal-fired plants (though air pollution for coal plants is still significant) and 6) Smaller quantities of leaves, trash and grass are being burned.

According to the US Environmental Protection Agency (EPA) website on “Air Trends” (http://www.epa.gov/airtrends/carbon.html) huge progress has been made in reducing levels of many outdoor air pollutants.  From 1980 to 2008, average outdoor carbon monoxide concentrations have been reduced by 79%, average particulates smaller than 10 microns in diameter (PM₁₀) fell by 31%, ozone fell by 25%, sulfur oxides fell by 71%, nitrogen dioxide fell by 46%, and airborne lead fell by an average of 78%.  Each of these pollutants was measured from 124 to 728 sites around the US- mostly in cities, suburbs and large towns.

However, the news on outdoor air quality is not all good.  Levels of outdoor airborne particulates, ozone and carbon monoxide are still high enough to increase risk of asthma, heart disease and stroke in many parts of the US.  Although outdoor air quality has improved dramatically in many US cities, indoor air quality is often bad due to such problems as inadequate outdoor ventilation, mold and water damage, and increasing use of pesticides and solvents.   Unfortunately, outdoor air quality is currently quite bad in many cities of the developing world such as Beijing and Mexico City.

Water quality has also improved in many parts of the country.  Water can be contaminated with a number of harmful agents including bacteria, viruses and protozoans, nitrates, petrochemicals like gasoline, pesticides and herbicides; and toxic metals such as mercury, lead and cadmium.

In the mid 20^th century, many US rivers and lakes were so polluted that little or nothing lived in or around them.  In the 1950’s and 1960’s Ohio’s Cuyahoga River had little aquatic life and was filled with floating oil, solvents and debris which caused 2 spectacular river fires in 1952 and 1969. Since the 1969 Cuyahoga Fire in Cleveland, several billion dollars of local, state and federal money have been spent to clean up the river and laws have been passed regulating industrial, domestic and agricultural waste discharges.  The improvement in Cuyahoga River water quality has been dramatic in this period.  By 2009, boaters have returned to the river and over 60 species of fish, bald eagles, blue heron and beavers have returned to the river. While the Cuyahoga still has some pollution problems (such as low levels of PCB= poly chlorinated biphenyls in the water and air pollution concerns in the Cuyahoga Valley), the Ohio EPA in 2009 removed large parts of the Cuyahoga from the list of impaired waterways.  Many other parts of the country have experienced large increases in lake and river fish populations following water cleanups.

Drinking water quality has also improved in many areas, although problems still exist.  Most studies have shown that pesticides, herbicides and solvent levels in ground, well and lake water sources have fallen in recent decades, although a few studies have reported increasing levels in some areas. Dramatic decreases in metal pollutants like lead, mercury and cadmium in drinking water supplies have also been reported in recent decades.  Levels of bacteria and viral contamination in drinking water sources have also been generally decreasing over the past decade.  In 1993, 1.6 million people were made sick from an outbreak of the protozoan (protozoan= one celled animal) Cryptosporidium in the Milwaukee drinking water supply. Levels of nitrate and phosphate pollution from agricultural operations have been decreasing in some areas and increasing in others.

Another point of concern is the presence of chemicals in water which mimic hormones like estrogen.   Such chemicals can increase risk of cancer and birth defects.  Such chemicals include pesticides, phthalate chemicals from plastics, synthetic hormone drugs like birth control pills, mycotoxins from molds and hormone mimicking chemicals from foods like soybeans.   Much more research on these hormone mimicking chemicals is needed.

Lead has been another important environmental success story. In the 1950’s and 1960’s, many US children and adults had high blood lead levels. Even moderately elevated blood lead levels have been significantly associated with many health and social problems, including learning problems, lower IQ, depression, attention deficit disorder, significantly higher rates of murder and other violence, and bone and heart problems.

 The biggest sources of lead exposure came from leaded gasoline, lead based paints and from lead smelting, mining and manufacturing.   In the 1970’s, lead was gradually phased out of gasoline, lead was removed from paint and many older homes had their lead paint removed/abated.  The health benefits of reduced lead exposure have been significant. From 1976 to 2006, the percentage of US children aged 1 to 5 years with high lead levels (above 10 micrograms per 100 milliliters of blood) have fallen dramatically from 80% to 2%.  A recent study reported that for every one dollar spent in removing lead paint from old homes, society saves at least $22 in increased school and work productively and reduced medical, educational and crime costs (Environmental Health Perspectives  July 2009; 117(7):1162-7).

Much work needs to be done to improve the environment.  The world is now facing pollution and energy pressures in much of both the developed and developing nations.  However, we should not lose sight of the fact that much progress has already been made on environmental matters.