Since the beginning of the Industrial Revolution, pollution has been a human and environmental health problem, yet little has been done at the federal level to address it until recent years.
In 1948, over a period of five days, a warm pocket of air trapped colder air over Donora, Pennsylvania. This led to a thick smog from nearby zinc and steel smelting factories. It caused the deaths of 40 people. Half the town of Donora -- about 14,000 people -- experienced respiratory and cardiovascular health problems.
As a result of this event and many others that led up to 1970, the United States declared the first Earth Day in response to increased public awareness of environmental issues caused by human activities.
Until the late 1960s and early 1970s, states had primarily dictated air pollution regulation, but as public concern steadily grew, the federal government began to step in.
In 1970, the U.S. government approved the Clean Air Act, which charged the Environmental Protection Agency, also called EPA, with identifying air pollutants from stationary and mobile sources that may reasonably be anticipated to have negative impacts on public health and welfare.
The initial list they came up with included:
By 1987, lead was added to this list as well, and in 2007 the U.S. Supreme Court ruled that greenhouse gases were also to be covered and managed by the Clean Air Act.
The Clean Air Act creates limits to the amount of air pollutants from mobile and stationary sources, as well as regions, that can be emitted:
|Type of Source||Clean Air Act Mandated Limit|
|Mobile||By 1975, automobile manufacturers must cut emissions by 90% in all new cars.|
|Stationary||The EPA must set performance standards for all major categories of stationary sources.|
|Regional||Regional limits must be met for ambient air quality in all regions and counties. Note that these limits do not vary by region, which makes it difficult for areas with higher amounts of pollution.|
As time has passed, standards have been added for newer sources of pollution. These standards are even stricter than past standards were for older sources at the passing of the Clean Air Act.
Based off of the Clean Air Act, the U.S. EPA sets the national standards for pollutants and their allowable levels. The EPA standards are geared at protecting public health and welfare against any known negative effects of listed pollutants.
As a result of regulation, improvements in air quality have been made. There has been a reduction in certain regulated pollutants, despite increases in energy use, vehicle miles traveled, and economic activity.
Causes of these improvements resulting from regulation and/or technology advancement are:
Levels of nitrogen oxides, sulfur dioxide, carbon monoxide, lead, and particulate matter have all decreased. Unfortunately, there has not been significant progress in ground-level ozone reduction.
Source: Adapted from Sophia instructor Jensen Morgan