Talk:Air quality index

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More details on how the air quality index is Calculated Needed?--Sfitzsi (talk) 15:44, 28 March 2009 (UTC)

It might be useful to add more details concerning the air quality index for ozone. In the US, for 8 hour average ozone, with concentration in units of ppbv, the breakpoints table is:

$C_{low}$	$C_{high}$	$I_{low}$	$I_{high}$	Category
0	59	0	50	Good
60	75	51	100	Moderate
76	95	101	150	Unhealthy for Sensitive Groups
96	115	151	200	Unhealthy
116	374	201	300	Very Unhealthy

I believe this information was provided earlier, as well as Canadian levels, but has been taken out. It is extremely salient, because US levels were changed in 2008 under Bush, and are under further scientific consideration now.

The values shown above for the US seem to be as proposed by the EPA, not as currently effective.

Problems with piecewise-linear interpolation

The discussion of piecewise-linear interpolation is somewhat garbled. The statement "At the boundary between AQI categories, there is a discontinuous jump of one AQI unit." is false for piecewise-linear interpolation. The whole point of piecewise-linear interpolation is to turn a set of breakpoints into a continuous function. This makes sense if the breakpoints in AQI are 0, 50, 100, etc. If they are 1,50,51,100,101, etc, this defeats the purpose of linear interpolation. It introduces the unnecessary complication of alternating very short and long intervals. Unless someone wants to completely rewrite this, the best way to minimize confusion and avoid giving a false impression of precision is to delete starting from the header "Computing the AQI" through the equations, insert a header "The EPA's table of breakpoints" just before the table, and delete the example after the table. I have done this below. Nothing in this article actually uses the linear interpolation formula, and it contributes only confusion. PiBVi (talk) 19:43, 1 July 2025 (UTC)[reply]