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Data from Second Set of Samples from PM2.5 Monitors

Release Date: 5/20/1998
Contact Information: For more information contact the Office of External Affairs at (214) 665-2200.

The U.S. Environmental Protection Agency (EPA) has obtained the second and third sets of results from fine particulate (PM-2.5) samples collected May 17-19 in four Texas cities. Sampling was in response to the heavy smoke and haze experienced in Texas due to extensive fires in Mexico and Central America.

The PM-2.5 concentrations below, which are given in micrograms of PM-2.5 per cubic meter of air (ug/m3), are for 24-hour periods of sampling.

                                          May 17-18                      May 18-19
Dallas                                    30.8 ug/m3                     32.5 ug/m3
San Antonio: site 1                       39.3 ug/m3                     27.5 ug/m3
San Antonio: site 2                       43.4 ug/m3                     27.4 ug/m3
Brownsville                               32.5 ug/m3                     31.7 ug/m3
Galveston                                 30.0 ug/m3                     27.5 ug/m3

The National Ambient Air Quality Standard for PM-2.5 is 65 ug/m3 for a 24-hour period and 15 ug/m3 for an average of all samples collected during a year. This standard is based on numerous health studies and reflects the concern about how very fine particulate matter interferes with lung function. Particles this small are more easily inhaled into the lungs and are more difficult to cough up.

Air samples analyzed to date reveal PM-2.5 levels less than the 24-hour health-based standard. These levels should not create a high health risk for most of the general population over a short period of time. Concentrations at or above these levels over many days may exceed the safe limit set for an average exposure during a year. Some people, including children, those with respiratory ailments and the elderly, are more sensitive to exposure. Sensitive people should exercise caution as outlined in the State's health advisory.

Additional data will be released by EPA as it is received.