Air Quality Bureau
High Levels of Particulate Matter in Doña Ana County
Health Effects and Cautionary Statements for High PM10
(Source: U.S. Environmental Protection Agency's rule (40 CFR 58, Appendix G) and guidelines ( download pdf file ) for air quality reporting) |
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| Serious risk of respiratory symptoms and aggravation of lung disease. | Everyone should avoid any outdoor exertion; people with respiratory disease, such as asthma, the elderly and children should remain indoors. | ||
| Significant increase in respiratory symptoms and aggravation of lung disease. | People with respiratory disease should avoid any outdoor activity; everyone else, especially children and the elderly, should avoid moderate or heavy exertion. | ||
| Increased respiratory symptoms and aggravation of lung disease. | People with respiratory disease, such as asthma, should avoid moderate or heavy exertion; everyone else, especially children and the elderly, should limit prolonged exertion. | ||
| Increasing likelihood of respiratory symptoms and aggravation of lung disease. | People with respiratory disease, such as asthma, should limit moderate or heavy exertion. | ||
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Federal Air Quality Standards for Particulate Matter
PM10 refers to suspended particles less than or equal to 10 microns in diameter. A micron is a unit of length equal to one-millionth of a meter; a PM10 particle is about one-seventh the diameter of a human hair. PM10 may include a variety of substances, including dust, smoke, and soot. PM10 particles are small enough to be inhaled deep into the lungs. High levels of PM10 can increase the number and severity of asthma attacks, cause or aggravate bronchitis and other lung diseases, and reduce the body's ability to fight infections. People most vulnerable to these effects include infants and children, the elderly, anyone who is exercising (because they breathe in more air, and therefore more particles), and those suffering from asthma or bronchitis.
The Federal Clean Air Act provides for the establishment of National Ambient Air Quality Standards (NAAQS) to protect the public from harmful levels of the most common pollutants in the ambient air. Ambient air is the outside air near ground level that people breathe. The standards are set on the basis of health studies and are designed to protect the health of susceptible individuals. State and local agencies regularly monitor the concentration of the pollutants for which there are national ambient standards.
The U.S. Environmental Protection Agency (EPA) has set standards for both
short-term (24-hr) and long-term (annual) average concentration of PM10.
Concentration of PM10 is measured in units of micrograms of particulate matter
per cubic meter of air (= ug/m3). The current standards, as revised in 1987,
are:
24-hour standard:
To meet this standard, the 3-year average of the number of 24-hour values
greater than 150 ug/m3 must be less than or equal to one. Since the measured
values are to be rounded to the nearest 10 ug/m3 (154 rounds down to 150, 155
rounds up to 160), the standard concentration is effectively 154 ug/m3. If
24-hr values are not measured every day or almost every day in a year, then
the number of exceedances is adjusted for sampling frequency. For example, if
sampling is done every 6th day, then one measured exceedance in a year counts
as six expected exceedances.
Annual standard:
To meet this standard, the 3-year average of the annual mean PM10 values must
not exceed 50 ug/m3. Annual means are determined by averaging 24-hr values in
each quarter, and then averaging the quarterly means to obtain an annual
value.
STANDARDS FOR COARSE AND FINE PARTICULATE MATTER
EPA periodically reviews the scientific data on health and environmental
effects of major pollutants to determine if the existing standards are
sufficient to protect public health. In July 1997, following the
recommendations of the most recent review of particulate matter health
effects, EPA retained the 1987 standards for PM10 in slightly revised form and
issued new ambient standards for fine particulate matter less than 2.5 microns
in diameter (PM2.5).
EPA issued a separate standard for PM2.5 because there are differences in
origin, composition, and health effects between the fine fraction (less than
2.5 microns in diameter, PM2.5) and the coarse fraction (mostly 2.5 to 10
microns) of PM10. In urban areas, particles in the fine fraction (PM2.5) are
produced primarily by fuel combustion, consist of both solid and liquid
droplets of sulfates, nitrates, and organic compounds, and are hazardous to
health in lower concentrations than the coarse fraction of PM10. The coarse
fraction commonly originates from dust, often consists mostly of mineral
particles found in earth, rock and
soil, and causes adverse health effects only at higher concentrations than the
fine fraction. Although most of the mineral dust in the air during dust storms
is larger than 2.5 microns, about 10-15% of the PM10 is smaller than 2.5
microns. Since the PM2.5 standard concentration is 65 ug/m3, PM10 levels
during dust storms have to be extremely high for the PM2.5 standard to be
exceeded.
Implementation of the new 1997 particulate matter standards was blocked by a
court case in 1999.
The New Mexico Air Quality Bureau and other air quality agencies nationwide
began monitoring PM2.5 in 1998. PM2.5 is currently being monitored on a daily
basis at several sites in Doña Ana County. A few of the most extreme dust
storms have resulted in exceedances of the 24-hr PM2.5 standard concentration,
but not enough to cause the standard to be violated.
USEPA
Information on the web about the standards for particulate matter,
the review process leading to new standards, and the court case.
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What caused the High PM10 Levels?
All but a few of the exceedances of the PM10 standard in Doña Ana County are caused by windblown dust raised by high winds. During dust storms, high winds cause dust to become airborne from areas with exposed dry soil, including the surrounding desert, dirt roads, and areas disturbed by construction or other earth-moving activities. EPA's Natural Events Policy allows for exceedances caused by high wind to be excluded from determinations of attainment status, provided certain requirements are met. One requirement is that NMED must provide evidence to support their conclusion that the exceedances flagged for exclusion were indeed caused by high wind. Such evidence usually consists of weather records, but may include other records such as satellite images, time-lapse video photography, and news reports of major dust storms. We plan to issue these reports on a quarterly schedule. Previous reports are listed below:
January 1995-March 1997
Summary (1 page) (download
pdf file)
Full report (111 pages): paper copy available by request
January 1997-June 2000
Body of report (10 pages)
(download pdf file)
Appendix (209 pages): paper copy available by request
July 2000-March 2001 (download pdf files)
Body of report
Appendix 1: Best Available
Control Method Letters from the City of Las Cruces, Doña Ana County, and
Primary Stakeholders
Appendix 2: Time Series
Plots of PM10 and Wind Speed
Appendix 3: Plots of
Hourly Average PM10 in Relation to Wind Speed
April 2001-June 2001 (download pdf files)
Body of report
Appendix 1: Best Available
Control Method Letters from the City of Las Cruces, Doña Ana County, and
Primary Stakeholders
Appendix 2: Time Series Plots of PM10 or PM2.5 and Wind
Speed
Part
1
Part
2
Appendix 3: Plots of
Hourly Average PM10 in Relation to Wind Speed
Appendix 4: Additional Supporting Data for Atypical
High-Wind Exceedances
Part
1
Part
2
July 2001 - September 2001 (download pdf files)
Body of report
Appendix 1: Best
Available Control Method Letters from the City of Las Cruces, Doña Ana
County, and Primary Stakeholders
Appendix 2: Time Series
Plots of PM10 or PM2.5 and Wind Speed
October 2001-December 2001 (download pdf files)
Body of report
Appendix 1: Best
Available Control Method Letters from the City of Las Cruces, Doña Ana
County, and Primary Stakeholders
Appendix 2: Time Series
Plots of PM10 or PM2.5 and Wind Speed
Appendix 3: Plots of
Hourly Average PM10 in Relation to Wind Speed
Appendix 4: Additional
Supporting Data for Atypical High-Wind Exceedances
January 2002-March 2002 (download pdf files)
Body of report
Appendix 1: Documentation
for Exceedence January 10, 2002, Anthony
Appendix 2: Documentation
for Exceedence February 21, 2002, Anthony
Appendix 3: Documentation
for Exceedence March 14, 2002, Sunland Park
Appendix 4: Documentation
for Exceedence March 21, 2002, Chaparral
April 2002-June 2002 (download pdf files)
Body of report
Appendix 1: Documentation
for Exceedence May 13, 2002, Anthony
Appendix 2: Documentation
for Exceedence June 7, 2002, Roadrunner & West Mesa
Appendix 3: Documentation
for Exceedence June 14, 2002, Anthony & Chaparral
Appendix 4: Documentation
for Exceedence June 28, 2002, Sunland Park
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Effects| Federal Standards| Causes| Related Topics