Mecklenburg County, North Carolina
State of the Environment Report, 1997

Contents | Agency Acronyms | Acknowledgements | Introduction | Executive Summary | State of the Air | State of the Water | State of the Land | Issues and Recommendations | Appendix A | Appendix B | Appendix C | Appendix D | Report Cover Page | About MCDEP | MCDEP Home Page

STATE OF THE AIR

(Air Environmental Indicators)

Air pollution is an environmental and human health issue and its effects impact large and small geographic areas. To this end, this chapter discusses the state of air quality in Mecklenburg County as it is reflected in ambient air monitoring data, inspections and compliance information, and nuisance, odor and dust complaints. In addition, this chapter provides a discussion of general indoor air issues. Where relevant, trends related to air quality are identified and discussed. A reference table also provides a quick summary of important environmental indicators related to Mecklenburg County's air.

Ambient Air

The air surrounding us or "ambient air" carries countless substances - both natural and man-made in origin. The various physical and chemical properties of these substances are major factors determining the quality of our air. Natural air pollution sources include gaseous emissions from trees, animals and lightning and gaseous and particulate emissions from volcanic eruptions and forest fires. More relevant to Mecklenburg County are our activities which create the man-made substances. These activities are generally categorized into either point, area or mobile sources. The relative contribution of each man-made source category is displayed on Table A-1 and Figure A-1 and is based on a complete 1996 emissions inventory for Mecklenburg County.

Point sources are stationary industrial sources such as manufacturing plants, gasoline terminals or printing operations engaging in processes that emit pollutants to the air. Among the point, area and mobile categories, point sources contribute the least amount of total pollutants, but often the most toxic. It should be noted that the amount of emissions attributable to point sources is reduced significantly by pollution control equipment or pollution prevention practices, many of which are required by federal and local regulations. Being stationary and easily quantified, point sources receive the greatest amount of regulatory attention.

Area sources are usually sources whose emissions, although small in and of themselves, can be quite significant because of their number. Area sources include consumer use of solvents, dry cleaners, gasoline service stations and household fuel combustion. Nearly 250 gasoline service stations held air quality permits in Mecklenburg County in 1997. Mecklenburg County emission inventories show that area sources contribute a large percentage of the total emissions, especially volatile organic compounds. Prior to the 1990 Clean Air Act Amendments, there were no regulations for area sources. The USEPA is now promulgating emission standards, many of which are likely to incorporate requirements for controls and work practices. Dry cleaners and companies which chrome-plate are the first of the area sources having specific requirements to reduce air emissions.

Automobiles, trucks, planes, trains, boats and any other non-stationary sources form the mobile source category. When considering air pollution as the total of all air pollutants, Mecklenburg County emission inventories indicate that mobile sources contribute more air pollution than either the point or area emission source categories. Indications are that the same distribution among the air pollution categories occurs throughout most of the state. For this reason, the USEPA and North Carolina have set tail-pipe emission standards for different pollutants, fuel specifications, and state-wide control measures at gasoline service stations. Other efforts focused on voluntary trip reduction techniques, car pooling and mass transportation are being promoted by many local, state and federal agencies. To be successful in reducing air pollution, all these efforts mean an individual must change certain aspects of their lifestyle and transportation. In addition to changing travel habits, improved mass transportation for Mecklenburg County has definite tax implications. To date, voluntary efforts to significantly reduce air emissions from mobile sources through a modification in lifestyle and transportation have been unsuccessful.

The USEPA has established National Ambient Air Quality Standards for six (6) major air pollutants: sulfur dioxide (SO2), particulate (PM-10), carbon monoxide (CO), ozone (O3), nitrogen dioxide (NO2), and lead (Pb). The PM-10 standard only includes particles with an aerodynamic diameter less than or equal to 10 microns, known as PM-10. It is generally felt that particulates with a greater diameter will not remain in the air long enough to be a significant air pollution concern. These six pollutants are referred to as "criteria" pollutants. A geographic area such as a county or metropolitan statistical area is designated either as an "attainment" or "nonattainment" area for each of the six (6) criteria pollutants, depending on the ambient air concentrations of each pollutant over a specified period. Historically, carbon monoxide and ozone have been the pollutants with the most exceedances of ambient air standards in Mecklenburg County.

New in 1997 and of potential significance to Mecklenburg County are changes to the particulate and ozone ambient standards. Though the cost versus benefit is still being debated in Congress, USEPA amended the particulate and ozone standards to be more stringent, meaning that less pollution will be needed for a geographic area to be classified nonattainment for the standard(s). A second category of particulate for particles with an aerodynamic diameter less than or equal to 2.5 microns or PM-2.5 was developed. Compliance for the PM-2.5 must be achieved beginning the year 2012, but reductions in ambient emissions must begin in 2005, should Mecklenburg County exceed the standard. As is the case for most of the country, Mecklenburg County will not know how great current PM-2.5 levels are until additional ambient air monitoring equipment is installed and operating. The ozone standard was changed to a lower concentration (.08ppm instead of .12ppm), but the measurement will occur over eight hours instead of a one hour period of time. The new ozone standard will require compliance required starting in 2005. A further explanation of the new ozone standard is found under the heading of "Ozone" in this Chapter.

The National Ambient Air Quality Standards or "NAAQS" were developed to protect public health and welfare and the environment. These standards are based on each of the previously mentioned six (6) criteria pollutants and are measured using procedures and units not easily understood by most persons. For this reason, a national reporting system known as the Air Quality Index was developed to communicate ambient air conditions to the public. The index is divided into five (5) general descriptions of "good", "moderate", "unhealthful", "very unhealthful," and "hazardous" to indicate the current status of ambient air quality. The descriptions are assigned using a numeric scale with 0-50 titled as (good), 51-99 (moderate), 100-199 (unhealthful), 200- 299 (very unhealthful) and 300-500 (hazardous). A numeric representation of the ambient air quality is calculated as the ratio between the highest monitored value of the daily, 8-hour, or 1-hour intervals and the NAAQS. Table A-2 displays the range of Air Quality Index values as well as corresponding advisory statements and potential health effects. Mecklenburg County index levels have never exceeded the unhealthful range, with most reports indicating the air quality to be good or moderate.

In Mecklenburg County, index calculations from April to October are usually based on ground-level ozone, while November to March values usually reflect carbon monoxide concentrations. Figure A-2 displays the number of "good" air quality days in 1997 as determined by the Air Quality Index. The seasonal effects of ozone and carbon monoxide pollution on air quality are further reflected in Figure A-3 which displays the Air Quality Index for 1997 in Mecklenburg County.

The overall ambient air quality in Mecklenburg County has steadily improved since 1980. Figures A-4 and A-5 illustrate the annual average Air Quality Index trend as well as the number of "good" days for the 1980-1997 period.

The Air Quality Index values for Mecklenburg County at any given time are based on ambient air monitoring levels in the County. Mecklenburg County has maintained an air pollution monitoring network since the 1960s. Currently, the County monitors carbon monoxide, ozone, nitrogen dioxide, total suspended particulate, and PM-10. The air quality monitoring network consists of five (5) carbon monoxide sites, five (5) PM-10 sites, three (3) ozone sites, one (1) sulfur dioxide sites and one (1) nitrogen dioxide site. Figure A-6 displays all current locations of monitoring sites within the County.

Ozone

Ozone is a clear gas with a bluish tint at higher concentrations. Unlike most other pollutants, ozone is not directly emitted into the atmosphere from a stack or vent; rather, it forms in the lower atmosphere as chemical reactions between volatile organic compounds and nitrogen oxides occur in the presence of sunlight and high temperatures. Due to the interaction of sunlight and heat, peak concentrations of ozone usually occur during the afternoon hours, especially of warmer summer days.

Ozone is the principal component of urban smog. Ground-level ozone or tropospheric ozone should not be confused with the ozone layer in the stratosphere, which is about ten miles above the earth's surfaces. Stratospheric ozone is beneficial to humans and the environment because it shields the earth from ultraviolet light which, at high levels, may cause increased incidence of certain skin cancers and cataracts, suppression of the immune system, damage to plants and aquatic organisms, increased formation of ground-level ozone and increased weathering of outdoor plastics. There is evidence that stratospheric ozone or the "ozone layer" is being depleted by the release of chlorofluorocarbons (CFCs) such as freon. This "ozone hole" occurred first over the poles, but is said to be enlarging as the depletion continues.

Ground-level ozone is most harmful to children, the elderly, people with respiratory illnesses and those who exercise vigorously. Ozone can irritate a person's eyes, nose and throat. Also, elevated ozone levels decreases the volume of air that can be brought into the lungs. Even at low concentrations, ozone affects vegetation and has frequently caused significant crop yield losses and plant damage.

In 1995, Mecklenburg County was officially designated as an attainment area for the ozone standard. In 1997 there were no exceedances of the National Ambient Air Quality Standard for ozone ( currently 0.12 ppm or an Air Quality Index less than 100) and the County remains an attainment area. The federal air quality regulations allow one (1) exceedance of the standard per year per monitoring site in each air quality control region.

Figure A-7 indicates Mecklenburg County's ozone design value has remained stable and slightly below the national standard (.12 ppm) since 1991. The design value is the single number representing the ozone level for the year and is used to determine an areas attainment status. It is somewhat complicated to calculate and is the fourth-highest value when averaging the monitoring data each sixty minutes on a continual or "rolling" basis.

Since Mecklenburg County remains close to the ozone standard and with a new stricter ozone standard to be effective in 2004 and compliance beginning in 2005, a return to a nonattainment designation is very possible. Figures A-8 a & A-8b compare 1997 ozone ambient air monitoring data to the old and new standards, and based solely on past ozone levels, Mecklenburg County will not comply. For continued improvement in air quality and to maintain our attainment designation, additional control measures will likely be necessary. Future ozone control strategies shall include stricter standards for sources of nitrogen oxide emissions and the effects of ozone transport from one region to another. Specific areas being examined for reductions in ozone are vapor collection when consumers fill their automobile gas tanks, cleaner burning gasoline, more sophisticated automobile tailpipe emissions tests, increased controls for utility power plants in neighboring counties, and the addition of controls for industries emitting pollutants in amounts less than what previously required controls. Currently the State is conducting studies and computer modeling to predict which controls will give the greatest benefit considering pollution reduction and cost.

An environmentally aware public will be a key in the success in reducing ozone levels and maintaining our federal attainment status. With this in mind, activities to heighten local citizen and industry's knowledge and involvement in air quality issues was promoted by state and local air agencies during 1997. Educational efforts such as the "Spare the Air... OZONE ACTION" ozone forecasting program (see highlight box page 61) began in the spring. This along with a series of radio and television advertisements provided information and useful suggestions accenting the expression that air pollution is everyone's problem and it will take everyone to solve it. Attracting attention to air pollution can have an entertaining and somewhat innovative approach. Several days during the summer ozone months of June, July, and August a hot air balloon with the "Spare the Air" banner and telephone number for MCDEP was aloft promoting ozone awareness.

Spare The Air... Ozone Action

In 1995, Mecklenburg County was officially designated as an attainment area for the national ground-level ozone standard; however, since then, levels above the national standard have occurred several times. As a result, only one day above the standard in 1997 could have required the State to implement the federally approved contingency plan, imposing additional controls on industry and the refueling of automobiles.

Since automobiles are one of the primary sources of pollutants which combined with the summer sun form ozone or smog , a voluntary employee education program was developed by the members of a Regional Air Quality Coalition. The program is called "Spare the Air... OZONE ACTION", and coalition members (representatives from government and business in this region) agree to educate their employees about how ozone is formed and what action regarding the use of their automobiles and other individual activities can prevent ozone formation.

From May 19 until Sept. 5, 1997 (summer ozone months), state meteorologists predicted when the conditions were conducive for the formation of ozone. The various levels of ozone were categorized by color, with green indicating low levels of ozone, leading to yellow, orange and red as the highest level of ozone predicted. Table A-3 provides the various ozone level categories and the corresponding numeric values in both the scale used by the monitoring equipment to determine the concentration of ozone which is parts per billion (PPB) concentration and the scale often provided in the local news and weather reports - the air quality index (AQI). Employees were notified on days when ozone formation was expected to be in the yellow or higher category and asked to take the prearranged voluntary actions. The actions included: bringing lunch to work to minimize driving during the hottest part of the day; combining trips and consolidating errands; commuting at non-peak times to avoid engine idling while waiting in traffic, and not using drive-through windows. Table A-4 illustrates the accuracy of the meteorologists predictions during the 1997 ozone season.

A pre- and post-survey was conducted to measure the effectiveness of the program. The results show that there was an 11% increase in awareness that air pollution is a problem in this region. An additional 14% of the people surveyed said they would take additional measures that might reduce air pollution.

The "Spare the Air" campaign will continue its important role in educating and coordinating the public's efforts to lower air pollution emissions and the formation of ground-level ozone. If you would like more information or would like to become involved in the coalition, please call the Spare the Air Hotline at (704) 336-6859. The hotline is available between May and September.

Carbon Monoxide

Carbon monoxide (CO) is produced by the incomplete combustion of fossil fuels. It is a colorless, odorless gas and can pose a danger from localized concentrations found on traffic-congested city streets. Carbon monoxide levels increase during winter months, primarily due to starting automobile engines in cold conditions. Atmospheric temperature inversions during the rush-hours of the winter months compound the problem due to limited pollution dispersion. Carbon monoxide is undetectable without monitoring equipment.

When inhaled, carbon monoxide enters the bloodstream and reduces the body's ability to deliver oxygen to the body's organs and tissues. At low concentrations, carbon monoxide causes fatigue and impairs mental functions. Under acute conditions, carbon monoxide intoxication may result in death. The effects of carbon monoxide exposure are especially serious for those who suffer from cardiovascular disease.

Figure A-9 displays the trend in the eight-hour design value for the period 1986-1997. The design value represents the second-highest monitored value. Mecklenburg County has not experienced a violation of the carbon monoxide standard since 1986 or an exceedance of the standard since 1990 despite a steady growth in automobile registrations and vehicle-miles-traveled (see Table A-1). Less polluting engines found in newer vehicles is the main factor accounting for the improvement in air quality. Mecklenburg County was officially designated as a carbon monoxide attainment area in 1995.

Other Ambient Air Pollutants

Since the establishment of the National Ambient Air Quality Standards in 1977, Mecklenburg County has not had a violation for the four (4) other ambient air pollutants: nitrogen dioxide, sulfur dioxide, PM-10, and lead. Monitoring data indicate improving or stable pollution trends for these pollutants, and their compliance status with the National Ambient Air Quality Standard is not expected to deteriorate in the near future.

Suspended fine particles (PM-10) are generated by many human activities and natural events. Because of their small size, PM-10 can easily be inhaled and penetrate into the body. Health effects from PM-10 exposure depend on the type and amount of particles inhaled and vary from respiratory aggravation to the development of cancer. PM-10 monitoring since 1989 indicates levels consistently below the National Ambient Air Quality Standard (Figure A-10).

Increased sulfur dioxide concentrations can affect public health (primarily as a respiratory irritant), the environment (damage to crops, acid rain) and visibility (suspended sulfate particulates). Ambient monitoring for sulfur dioxide in Mecklenburg County began in the mid-1960s but was discontinued in 1984 due to very low levels. Monitoring resumed in 1994 and has indicated compliance with the annual, 3-hour, and 24-hour standards for sulfur dioxide levels (Table A-5). The continued use of low-sulfur fuels should assure the County of low ambient levels in the future.

Occurring in the environment primarily as a waste gas from fuel combustion, nitrogen dioxide can affect the respiratory system of children and asthmatics at concentrations as low as 0.5ppm and, like sulfur dioxide, can lead to crop damage and acid rain formation. Ambient monitoring for nitrogen dioxide began in the mid-1960s but was discontinued in 1986 because of low concentrations. Monitoring was resumed in 1989 due to recent studies emphasizing the role of nitrogen dioxide in the formation of ozone. It has been suggested that nitrogen dioxide may the one component among the several necessary for ozone formation which determines the amount of ground-level ozone created. Nitrogen dioxide levels have remained steady and are not likely to exceed the National Ambient Air Quality Standard; however new control strategies for limiting ozone formation will likely involve reducing nitrogen oxide emissions from industrial sources. Figure A-11 displays the 5-year trend for nitrogen oxide levels.

Lead has never been monitored routinely in the County; however, a study conducted in 1982 analyzed the lead content of total suspended particulate filters collected from thirteen (13) sites. This data and subsequent random sampling has revealed concentrations that are well below national standards.

Air Toxics

The term "air toxics" applies to certain chemicals that adversely affect the environment and/or human health when airborne and inhaled. A substance is defined as an "air toxic" if it is poisonous, an irritant or known or suspected to cause cancer. Both the State of North Carolina and the USEPA regulate air toxic emissions. The State of North Carolina has identified 105 "toxic air pollutants," while the USEPA has established a list of 188 "hazardous air pollutants." Air toxics can be natural chemicals or industrial by-products and are emitted in greatest quantities by many different industrial processes. As such, air toxics present more localized, site-specific pollution and human health problems. Some air toxics are also volatile organic compounds (VOC) and can therefore affect ambient air quality by contributing to the formation of ground-level ozone (smog).

Assessing and communicating the risks associated with air toxic emissions is difficult. There are many factors involved in assessing risks involved with exposures to air toxic: exposure time, degradation of a chemical over time, inhalation dosage, chronic (long-term) versus acute (short-term) health effects, and the tendency of a toxic to accumulate in plants and animals. Each of these factors needs to be considered and understood when determining potential adverse health or environmental effects.

In 1994, an inventory was made of the top ten (10) air toxics emitted into the atmosphere from industrial facilities which are required to have air quality permits and located in Mecklenburg County. From this inventory, seventeen facilities were identified as large emitters of regulated toxic air pollutants. Of the seventeen identified, six (6) had already demonstrated (either in 1994, 95 or 96) using USEPA approved computer models, that levels of toxic air pollution were below the acceptable ambient level. During 1997, the other eleven of these seventeen facilities were asked to voluntarily conduct computer modeling. Seven (7) facilities conducted the modeling with all demonstrating acceptable ambient levels. The remaining four (4) facilities either postponed the modeling until 1998, at which time the modeling will be required due to facility modifications, or the facility reduced toxic air emissions to a less significant level or are still considering the request. In coming years most facilities will be examined for toxic and hazardous air emissions often including modeling, as Federal State and local regulations address new industrial construction, facility modifications and industry specific requirements.

Nuisance Odors, Dust, Smoke

People who work and live in Mecklenburg County sometimes experience localized air quality problems such as nuisance odors, dust, and smoke. In 1997, 114 air quality requests for service were reported by citizens of the County. Figure A-12 displays the location of all air quality service requests received in 1997 and the location of all permitted industrial sources. The distribution of these air quality service requests suggests that nuisance odors, dust, and smoke occur most frequently near industrial-related activities. There are approximately 299 permitted (regulated) industrial facilities in Mecklenburg County.

Of the 114 total air quality service requests received in 1997, approximately 62% involved concerns about odors. Nuisance odors are generated by many different types of industrial processes. The degree to which industrial process odors become a nuisance depends on several factors including prevailing weather conditions, individual sensitivities, amount released, and odor threshold of the pollutant involved. Reports of visible emissions or excessive smoke generated by a specific industrial facility were nearly 8% of the requests with the remaining 30% of the service request incidents involving miscellaneous problems such as dust, particulate deposition on property and over spray from painting.

Indoor Air

In order to enhance energy efficiency, many homes and offices have been made more air-tight. One consequence of this building construction is less air ventilation and a greater concentration of airborne pollutants. The average home or office may contain concentrations of carbon monoxide, nitrogen oxides, formaldehyde, particulate matter, tobacco smoke, benzo-a-pyrene, radon, pollen, and microorganisms. Except for industrial work places, indoor air pollution is not regulated.

In addition to the 114 outdoor air quality concerns reported in 1997, eight (8) indoor air quality problems were investigated. Air sampling and analysis was conducted in each of these instances due to medical concerns. These incidents consisted of complaints of unknown contaminants. Indoor air problems usually result from poor air ventilation but individual sensitivities, nature of the pollutant and exposure time are also important factors. Indoor air problems are frequently identified because of acute health effects such as headaches, dizziness or irritations. These acute effects lead many to assume, often incorrectly, that more debilitating or fatal effects will occur.

On a national level one of the more serious indoor air problems is radon. Radon is a colorless, odorless, radioactive gas that comes from the natural breakdown of uranium in rock and soil. As uranium decays, it produces radium which in turn releases radon gas. Once released, this gas seeps to the surface of the soil and into the atmosphere or a building through cracks in concrete floors and walls, floor drains, sumps, joints and pores in hollow brick walls. Prolonged exposure to elevated radon levels may lead to the development of lung cancer.

In 1990, a survey of fifty-five (55) Mecklenburg County homes found radon levels below the USEPA action level of 4piC/l. Based on this data, Mecklenburg County was classified in 1993 as a "Zone 3" area meaning radon levels are predicted to be less than 2pCi/l. Although no standard or limit has been established for radon exposure, the USEPA recommends corrective action if monitored levels exceed the action level. The USEPA also continues to recommend a radon test for every home.