|
|
FYI
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|
A particle of 2.5 microns is about 1/20th the width of a human hair, while a particle of 10 microns
is about 1/5th the width of a human hair.
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|
(Source: EPA, Health and Environmental Effects of Particulate Matter Fact Sheet,
July 17, 1997.)
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|
The category of air pollutants called "respirable particulate matter" includes liquids, hydrocarbons, soot, dusts, acids from
aerosols, and smoke particles that are smaller than 10 microns in diameter. This 10-micron size limit has led to the abbreviation of respirable particulate matter as "PM10." The
EPA has further divided these tiny particles -- which make up about 55 percent of the total mass of suspended particles in air pollution-- into "fine" particles of 2.5 microns or less and
"coarse" particles of between 2.5 and 10 microns.
While the nose can filter out larger particulates, PM10 and especially PM2.5 particles can penetrate deep into the lungs.
The farther a particle penetrates into the lungs and the higher the concentration, the more likely it is to cause
wheezing, nose and throat irritation, bronchitis, and lung damage. Toxic chemicals attached to respirable particulate
matter emissions can increase the potential for adverse health effects. Groups at high risk because of fine and coarse
particles include children, the elderly, and people with pre-existing heart or respiratory conditions like asthma and
emphysema. Beyond these health hazards, fine particles impair visibility throughout the United States and can discolor clothing and property.
In 1987 the EPA revised its air quality standards for particulate matter to cover particulate matter smaller than 10
microns. The EPA estimated that adherence to these new 1987 standards would save 3,600 lives, reduce lost work
days by 190,000 days, and cut down on "reduced-activity" (days when people work less efficiently because of ill health) by 910,000 days.*
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HIGHEST pm10 DAILY AVERAGES IN MAJOR METROPOLITAN AREAS, 1998-2000
|
|
|
1998
|
1999
|
2000
|
|
Austin
|
NA
|
52
|
50
|
|
Brownsville
|
100
|
87
|
NA
|
|
Corpus Christi
|
101
|
87
|
71
|
|
Dallas
|
66
|
59
|
54
|
|
Midlothian
|
100
|
50
|
58
|
|
El Paso
|
170
|
240
|
148
|
|
Fort Worth
|
48
|
43
|
44
|
|
Houston
|
126
|
115
|
102
|
|
Laredo
|
93
|
71
|
56
|
|
Lubbock
|
40
|
37
|
44
|
|
San Antonio
|
59
|
49
|
44
|
|
San Benito
|
61
|
58
|
58
|
|
Galveston/Texas City
|
80
|
44
|
66
|
|
Source: U.S. Environmental Protection Agency, AIRS Database, 2001
|
|
National Standard 155MG
California Standard 55MG
Note: The 99th percentile of readings
are used as the highest daily average between 1997-2000.
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|
In 1997 the EPA created a new separate standard for PM2.5 because it determined that the PM10 standard did not provide
adequate protection for human health.* It was the association between mortality due to cardiopulmonary diseases and
particulate-matter air pollution that spurred the EPA to adopt a specific standard for PM 2.5.* According to the EPA, the new
PM2.5 standard and its eventual implementation will save 15,000 lives, reduce the risk of hospital admissions by thousands, reduce the risk of respiratory symptoms in children,
and result in thousands fewer cases of child and adult asthma per year.* Based on these and other health and welfare
benefits, the EPA estimated annual savings of between $19 and $104 billion in 2010, compared with annual pollution control costs of only $8.6 billion.* However, recent court cases have put implementation of this standard on hold.
In Texas, only El Paso County has repeatedly exceeded the 24-hour standard set in 1987 for PM10. Other areas -- such as
Lubbock -- have occasionally exceeded the 24-hour standard.*
In El Paso, particulate matter levels rise during winter months, due mainly to combustion of wood and other fuels for heating. These violations of the particulate standards exposed El Paso
County's "at-risk" population to high PM10 concentrations in the 1990s. Other Texas "at-risk" populations that have been exposed to PM10 levels that exceeded the tougher California
PM10 standard of 50 micrograms per cubic meter (vs. the federal standard of 150 micrograms per cubic meter) include residents of Webb, Cameron, Dallas, Harris, and Galveston
counties, among others.
Six Texas communities -- El Paso, Houston, Beaumont, San Antonio, Corpus Christi, and Dallas -- have begun a special
air sampling study of respirable particulate matter 2.5 microns or less in size. The fine particulate monitoring project is
being used to forecast whether high levels of particulate matter in excess of the new standard are expected.
Preliminary data from 1997 show that Houston, Dallas, and Corpus Christi have the highest average daily levels.* The
EPA estimates that levels from 1993 to 1995 demonstrate that, among Texas cities, only Houston and Corpus Christi currently appear to face difficulty meeting the annual PM2.5 standard.*
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COMPARISONS OF HIGH 24-HOUR AND ANNUAL PARTICULATE MATTER STANDARDS IN MONITORS IN
CIUDAD JUAREZ AND EL PASO, 1995
|
|
SITE NAME
|
24-HOUR HIGH
|
24 HOUR
EXCEEDENCES
|
ANNUAL AVERAGE
|
ANNUAL
EXCEEDENCE
|
|
Tillman*
|
144
|
0
|
35.9
|
No
|
|
Vilas*
|
143
|
0
|
46.8
|
No
|
|
Camizal*
|
84
|
0
|
18.7
|
No
|
|
Socorro*
|
178
|
6
|
38.1
|
No
|
|
Zenith Corporation+
|
1000
|
18
|
90.6
|
Yes
|
|
Advanced Transformer+
|
294
|
74
|
118
|
Yes
|
|
Technical Institute+
|
156
|
6
|
46.7
|
No
|
|
Source: Texas Natural Resource Conservation Commission, Air Monitoring Report 1995 (April 1997).
|
|
24-hour Standard 155 ug/m3
One-year Standard 51 ug/m3
*El Paso 1995 Levels
+Ciudad Juarez 1995 Levels
|
|
El Paso is impacted by particulate matter drifting in from Ciudad Juárez. Common sources of this
particulate matter include numerous unpaved roads and industrial combustion processes, such as the incineration of garbage, including tires, without adequate controls. In
fact, PM10 monitors in Mexico have continually registered 24-hour levels exceeding standards just across the border from El Paso. Nonetheless, these levels are often not valid for
comparison to U.S. standards because of the incompleteness of samples.* In addition, without
adequate emissions inventories and ambient air quality monitoring in Ciudad Juárez designed to record air quality over time, it is difficult to determine if emissions are going down. |
