The Clean Air Act (CAA) is a piece of US federal legislation that attempts to comprehensively regulate air emissions released by area, stationary, and mobile sources. The original Act also called for the EPA to establish National Ambient Air Quality Standards (NAAQS) to protect public health and the environment.

The goal of the original Clean Air Act of 1970 was to create and meet NAAQS in every state in the union by 1975. The Act was amended in 1977 when this ambitious deadline was far from being met in most of the states. The Act was again amended in 1990 to account for the formerly unregulated issues of acid rain, ground-level ozone, stratospheric ozone depletion, and various air toxics.

The Act and its amendments are divided into several subchapters, also called titles, that cover various aspects of air pollution.

Subchapter   I   - Programs and Activities
Subchapter  II   - Emission Standards for Mobile Sources
Subchapter III   - General Provisions
Subchapter  IV   - Noise Pollution Provisions
Subchapter  IV-A - Acid Rain Provisions
Subchapter   V   - Permiting Requirements
Subchapter  VI   - Stratospheric Ozone Protection

Clean Air Act

As noted above, the US lead the charge for clean air by passing the Clean Air Act in 1970, but what did other nations do to play catch-up? Well, the UK passed their own Clean Air Act some fourteen years later earlier. (Dratted British always showing us up.)

The Clean Air Act of 1956

(An Act to make provision for abating the pollution of the air.)

Prompted by the Great Smog of 1952 in London, this bill focused largely on causes of smog.

The bill put restrictions on the productions of 'dark smoke' (because everyone knows that if you can't see the pollution then it can't hurt you), required new furnaces be able to run 'smokelessly' (I can't see any smoke so it must be non-polluting!) and have an approved grit and dust removal systems, allows for the creation of smoke control areas, provides grants to help switch from coal stoves to cleaner heating systems, and mandates tall chimneys/smoke stacks on certain buildings (exceptions: residences, offices, and shops)¹.

('Wait!' I hear you say. 'Isn't that last bit just about dirtying up the air somewhere else?' Yes, but if we spread the pollution out, it's not too bad, see? Anyway, there's nothing out there but a bunch of nature. Nature doesn't vote.)

The Clean Air Act of 1968

An Act to make further provision for abating the pollution of the air.

Okay, they didn't quite get it right the first time. So in 1968 the bill was amended to, more than anything, expanded the tall chimney/smoke stack mandate to include pretty much all buildings.

When this Bill was introduced in the Commons it was hoped to be able to include statutory provisions against the emission of fumes, but it became clear that fume control is still imperfect and extremely expensive The best way of coping with this problem at the moment is by having chimneys which send the fumes high enough so that by the time they come down they are so diluted that they can be more or less disregarded as a health hazard or a nuisance. This technique is extremely successful. One of the most troublesome gases is that of sulphur dioxide, which turns into highly corrosive sulphuric acid. -- Lord Raglan to the House of Lords, 27 May 1968

This is a very effective way indeed of reducing pollution in urban areas such as London (where all the voters are). Okay, sure, those taller smokestacks might just result in all that sulfuric acid falling back down as acid rain over in Scandinavia, which rather mucks up their formerly-beautiful forests, but remember: Scandinavians (and doubly so, Scandinavia's trees) don't vote in England's general election. More spreading out of pollution, you see?

The bill also restricted the sale of prohibited fuels in the smoke control areas, and applied to large particulate ('grit and dust') restrictions to significantly smaller furnaces (100lb/hour rather than 1 ton per hour).

This solves forever the problem of pollution, through the brilliant combination of stopping visible pollution and exporting to the north the other pollution. But, wait! We need to look like we're doing something. Let's make a new act!

The Clean Air Act of 1993

(An Act to consolidate the Clean Air Acts 1956 and 1968 and certain related enactments, with amendments to give effect to recommendations of the Law Commission and the Scottish Law Commission.)

(This is the last one, I promise. We got it right this time, we're sure.) The subtitle pretty much explains it. This combined the bills into one big bill. (I told you we got it right! Let's just make some minor adjustments and refactor.)

(Seriously, though, these bills did reduce pollution a lot, but we should probably be glad it's not the only clean air legislation to come out of Britain.)

Sources

• http://www.statutelaw.gov.uk/content.aspx?activeTextDocId=1229602&versionNumber=1
• http://www.statutelaw.gov.uk/content.aspx?activeTextDocId=1204419&versionNumber=1
• http://www.opsi.gov.uk/ACTS/acts1993/ukpga_19930011_en_1
• http://hansard.millbanksystems.com/lords/1968/may/27/clean-air-bill
• http://en.wikipedia.org/wiki/Clean_Air_Act_1956

¹ Wikipedia mentions the moving of power plants to rural areas, but I see nothing about that in the act. Perhaps it was a result of smoke control zones.