Table 2.
Mean and Median PM2.5 Concentrations for each Year (µg/m3).
| Year | Mean (SD) | Median (IQR) |
|---|---|---|
| 1981 | 19.8 (5.93) | 21.2 (16.0–24.5) |
| 1982 | 17.5 (5.28) | 19.1 (14.3–21.6) |
| 1983 | 17.4 (5.55) | 18.5 (13.7–21.9) |
| 1984 | 17.1 (5.02) | 18.4 (14.0–21.0) |
| 1985 | 16.5 (4.88) | 17.6 (13.3–20.3) |
| 1986 | 16.0 (4.93) | 17.1 (12.7–20.0) |
| 1987 | 15.9 (4.89) | 16.8 (12.7–19.9) |
| 1988 | 15.7 (4.86) | 16.6 (12.5–19.7) |
| 1989 | 14.7 (4.66) | 15.9 (11.8–18.4) |
| 1990 | 14.9 (4.82) | 16.1 (11.5–18.8) |
| 1991 | 14.1 (4.38) | 14.7 (11.4–17.7) |
| 1992 | 13.1 (4.07) | 14.3 (10.7–16.4) |
| 1993 | 13.0 (4.14) | 13.8 (10.5–16.3) |
| 1994 | 12.6 (3.99) | 13.2 (10.2–15.9) |
| 1995 | 12.3 (4.09) | 13.1 (10.0–15.7) |
| 1996 | 11.9 (3.80) | 12.9 (9.85–15.0) |
| 1997 | 12.0 (3.87) | 13.1 (9.63–15.1) |
| 1998 | 12.3 (4.14) | 13.8 (9.49–15.7) |
| 1999 | 11.9 (3.83) | 12.6 (9.72–14.8) |
| 2000 | 11.4 (3.78) | 12.4 (9.36–14.5) |
| 2001 | 10.5 (3.14) | 11.3 (9.18–12.8) |
| 2002 | 10.0 (2.96) | 10.6 (8.64–12.4) |
| 2003 | 9.99 (3.05) | 10.8 (8.86–12.3) |
| 2004 | 9.79 (2.94) | 10.4 (8.55–12.1) |
| 2005 | 10.7 (3.41) | 11.8 (9.49–13.1) |
| 2006 | 10.1 (3.22) | 11.1 (8.23–12.6) |
| 2007 | 10.3 (3.32) | 10.9 (8.90–13.0) |
| 2008 | 9.02 (2.29) | 9.41 (8.25–10.7) |
| 2009 | 7.94 (1.96) | 8.43 (7.38–9.41) |
| 2010 | 8.53 (2.44) | 9.17 (8.01–10.3) |
| 2011 | 8.50 (2.29) | 9.04 (7.71–10.3) |
| 2012 | 7.63 (1.75) | 8.09 (7.00–8.84) |
Mean and median PM2.5 concentration (µg/m3) per year for US counties included in the analysis. (SD: standard deviation; IQR: interquartile range).