The federal ozone standard requires that ozone readings not exceed 85 parts per billion (ppb) over an eight-hour period. This new eight-hour standard provides increased protection to the public against a wide range of ozone-induced health effects.

To determine the eight-hour standard, the fourth highest daily eight-hour average per site for each of three years is averaged together. For example, site A's fourth highest eight-hour average was 85 ppb in 1997, 93 ppb in 1998, and 83 ppb in 1999. The three-year average would then be 87 ppb. Since this number is greater than 85 ppb, site A exceeds the federal standard.

The table below shows three year average of the 4th highest eight-hour ground-level ozone reading beginning in 2000 for each of the air monitoring sites operated by the Indianapolis Department of Public Works' Office of Environmental Services.

Overall, this table shows some positive trends.  As the conclusion of the 2005 season, central Indiana only has one site that now violated the 8-hour ozone standard (Noblesville).  This is encouraging considering that seven sites violated this standard in 2004.

Table:  Three Year Averages of the 4th Highest Eight-Hour Ground-level Ozone Readings by site (in ppb)

Site Number	Location	2000-2002	2001-2003	2002- 2004	2003- 2005
01	E. 16th St., Indianapolis	89	89	86	77
18	Fort Harrison, Indianapolis	90	92	88	81
19	Mann Rd., Indianapolis	84	81	77	71
20	Harding St., Indianapolis	86	84	79	73
25	Emporia	91	95	89	80
30	Fortville	92	94	88	81
32	Noblesville	93	96	92	87
39	Monrovia	88	85	82	77
40	Trafalgar	87	86	83	76
45	Whitestown	88	90	86	80
46	Avon	88	85	81	76
47	Plummer	89	88	84	80
48	Brownstown	85	85	80	75
50	Fairland	93	94	87	80

** Note: bolded numbers in the box indicate that the site exceeded the federal standard for that particular three-year average.

Please visit the Indiana Department of Environmental Management's website for more information about the origin and history of the eight-hour ozone standard.