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26 August 2011

Carbon monoxide poisoning

Countries around the world are taking steps to combat toxic air pollution. One of the leading sources of air pollution is carbon monoxide (CO). This colorless, tasteless, and almost odorless gas has been shown to affect human and animal health, as well as cause serious damage to the environment. Research shows that efforts to limit and eliminate this potentially harmful gas may be working. Government agencies, such as the Environmental Protection Agency (EPA), have worked to limit CO emissions and far-reaching national and international standards have been established. However, CO continues to be a serious problem. Due to the rapid development of developing nations, millions of new vehicles are adding to the levels of CO and other air pollutants. As such, a great deal of work remains to counter the effects of carbon monoxide.

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BACKGROUND

Countries around the world are taking steps to combat toxic air pollution. One of the leading sources of air pollution is carbon monoxide (CO). This colorless, tasteless, and almost odorless gas has been shown to affect human and animal health, as well as cause serious damage to the environment. Research shows that efforts to limit and eliminate this potentially harmful gas may be working. Government agencies, such as the Environmental Protection Agency (EPA), have worked to limit CO emissions and far-reaching national and international standards have been established. However, CO continues to be a serious problem. Due to the rapid development of developing nations, millions of new vehicles are adding to the levels of CO and other air pollutants. As such, a great deal of work remains to counter the effects of carbon monoxide.

Carbon is an essential element found in all living things. Carbon's chemical symbol is C; its atomic number is six. The compound carbon monoxide (CO) is produced when materials containing carbon are incompletely burned. Although it burns a bright blue near a flame, CO is generally invisible. Carbon undergoes a chemical transformation known as oxidation. This changes carbon into different forms; when a carbon atom attaches to an oxygen atom, CO forms.

CO is measured in parts per million (ppm). As of yet, universally set standards have not been established for indoor levels of CO. However, the U.S. National Ambient Air Quality Standards for outdoor air are 9ppm for eight hours, and 35ppm for one hour. In homes without gas stoves, average CO levels range from 0.5ppm to 5ppm. Homes with properly adjusted gas stoves typically have CO levels of 5-15ppm, while poorly adjusted stoves measure 30ppm or higher.

CO actually serves a variety of useful industrial and manufacturing purposes. It can be used in fuels, detergents, and compounds used to produce soft drinks, photography equipment, and food additives.

CO is released by multiple sources, including paint, paint removers, solvents, degreasers, tobacco smoke, charcoal grills, household appliances, propane heaters or stoves, space heaters, and gasoline- and diesel-powered generators. High CO levels are released by internal combustion engines, boilers and furnaces, and burning fuels, such as coal, charcoal, and wood. According to the Environmental Protection Agency (EPA), about 85-95% of all CO emissions may be caused by motor vehicle exhaust.

Since the time of the ancient Greeks, CO has been associated with poisoning. CO may have led to the 1875 death of author Edgar Allen Poe. A CO-related outbreak resulted in the deaths of 611 New Yorkers in 1927. In 1934, chronic CO poisoning almost killed polar explorer Richard Byrd. In the 1990s, Dr. Jack Kevorkian gained notoriety by using CO as a tool for medical suicide.

CO poisoning: Without proper ventilation, CO emissions can build up. This results in a condition known as carbon monoxide (CO) poisoning. Its effects can vary, depending on a person's age and overall health, as well as the concentration and length of CO exposure. CO fumes are considered harmful to the health of every human and animal. In particular, fetuses, infants, and people with cardiovascular or respiratory problems are susceptible.

At lower concentrations, CO poisoning and flu symptoms may seem similar; chest pain, confusion, headache, dizziness, weakness, and nausea and vomiting may develop. In most cases, these symptoms go away after the individual leaves the location of the CO emission. Higher levels of exposure may result in similar symptoms, as well as impaired vision and coordination, cardiovascular, neurological and respiratory problems, loss of consciousness, and death. Studies show that CO may be associated with increased numbers of allergies and asthma cases.

CO poisoning is the nation's leading cause of accidental poisoning deaths. The U.S. Centers for Disease Control and Prevention (CDC) estimate that about 500 people die due to CO poisoning annually. In addition, more than 2,000 may commit suicide through CO poisoning every year, and more than 15,000 people end up in hospital emergency rooms. The more CO present in the air, the more CO the body absorbs. As a result, oxygen may not be absorbed into the body, which may lead to tissue damage or death.

Medical treatment: If CO exposure is suspected, patients should see their physicians or healthcare professionals as quickly as possible. As flu and low CO levels share similar symptoms, physicians look for certain "red flags." These include the absence of a fever, any history of CO exposure, and similar complaints from multiple patients. Physicians may check for alcohol intoxication, smoke inhalation, trauma, and medical illnesses. All women of childbearing age suspected of CO poisoning should receive a pregnancy test. Physicians usually measure patients' levels of carboxyhemoglobin (COHb), a protein that interferes with oxygen's functions in the blood. Physicians must be informed of any clinical symptoms, as well as the patient's history of CO exposure. This helps to determine the proper treatment program.

If patients are diagnosed with CO poisoning, medical professionals administer 100% pure oxygen, which the patient inhales until the symptoms are eliminated. This is both the most common treatment option and the standard of care. Patients also receive periodic neurological exams to measure whether CO levels are decreasing. These exams also check for the development of cerebral edema (swelling of the brain). For COHb levels higher than 25-30%, patients may be given hyperbaric oxygen therapy (HBO), which is medical oxygen given at increased atmospheric pressure. With HBO therapy, the patient is placed inside a special chamber, in which they inhale the oxygen. Patients with very high CO levels may receive chest X-rays, magnetic resonance imaging (MRI) scans, or computed tomography (CT, CAT) scans. These scans provide images of the inside of the body.

Following treatment, discharged CO poisoning patients may be at risk for delayed neurological complications. Patients are advised to return for a follow-up medical and neurological exam within two weeks.

Environmental effects: CO is classified as one of six common and potentially harmful air pollutants, known as "criteria pollutants." The other five pollutants are: particle pollution (PM), ground-level ozone, sulfur oxides, nitrogen oxides, and lead. Studies suggest that criteria pollutants may cause serious harm to the environment, as well as human and animal health. Criteria pollutants may also cause major damage to structures and property. The Environmental Protection Agency (EPA) measures the levels of these pollutants in two ways: 1) the agency tracks outside air concentrations at selected American monitoring sites; and 2) the agency also tracks the estimated emissions of the total tons of airborne pollutants annually.

Greenhouse gases allow sunlight to reach the planet's surface directly. They then trap this energy within the atmosphere, heating up the planet's temperature. While CO is not considered a greenhouse gas, it is needed to produce two harmful air pollutants: methane and tropospheric ozone. Research suggests that while CO levels were rising until the late 1980s, they have since been declining. This may be due to the increased use of catalytic converters, which reduce vehicle emissions. CO also combines with other air pollutants to form smog, which is a murky, brown haze that may cause breathing and vision problems.

CO detectors: Healthcare providers and government agencies generally recommend that U.S. homes install at least one carbon monoxide detector (also known as a CO alarm). Many European countries and Canada encourage their use as well. These detectors are designed to warn people if CO levels accumulate to dangerous concentrations.

TECHNIQUE

Preventing carbon monoxide (CO) poisoning: There are simple steps people can take to reduce or avoid the build-up of CO in homes and other structures. There is currently no better known method for reducing and eliminating CO than removing potential sources of CO. It is very important to have proper ventilation, especially where pollutants are stored or used. Vented space heaters, stoves, ovens, or gas ranges are considered safer than un-vented models. Gas stoves should have an exhaust fan installed and vented to the outside. Wooden stove doors must fit tightly, and the selected wood should be properly sized and certified to meet the emission standards of the Environmental Protection Agency (EPA).

According to the EPA, an estimated 85-95% of all CO emissions may be due to motor vehicle exhaust. Internal combustion engines must never be located in attached garages, parking lots, nearby roads, or other confined areas.

All combustion equipment should be properly maintained and cleaned by qualified technicians annually. Combustion involves the burning of fuel to produce power; it is used in equipment such as boilers, water heaters, furnaces, heating systems, and chimneys. Any repairs, especially leaks, should be done quickly. Gasoline-powered and kerosene-powered equipment should be located and operated away from living areas. This is because running engines indoors has been shown to lead to CO accumulations, even when doors are kept open.

A 2004 study published in the American Journal of Emergency Medicine found that CO levels may be particularly dangerous when stoves are used for cooking and heating associated with outdoor activities. Individuals experiencing dizziness, light-headedness, or nausea, with suspected CO poisoning, should see their qualified healthcare professionals as soon as possible.

CO detectors: It is important to note that CO detectors are not the same as smoke detectors; smoke detectors only detect smoke particles. CO detectors are designed to warn occupants if pollutant levels accumulate to dangerous concentrations. These alarms test the air for CO every 1-3 minutes. These detectors should be equipped with loud alarms that are easily heard inside the home and garage.

As CO mixes freely with air, detectors can be installed at any height. They should be installed away from smoke detectors, as alarm sounds can overlap. When using CO detectors, it's best to ensure that there is enough venting. Homeowners should install CO alarms at least five feet from household chemicals and combustion devices, as they can damage alarm sensors. CO alarms can utilize battery-power, electrical systems, or a standard 110V electrical outlet. Alarms should be tested regularly and should be able to be reset easily. Battery-powered alarms should be tested weekly; the batteries should be replaced at least once a year. Hard-wired devices should be tested monthly. CO detectors are available at many stores and through utility companies.

Researchers are working to improve CO detection technology. Currently, CO detectors are not as reliable as smoke detectors. CO detectors may be unable to sense lower and possibly unhealthy CO concentrations, especially when the CO levels have been present in the nearby atmosphere for long periods of time. In addition, CO detectors can fail to go off at high concentrations. Therefore, removing CO sources remains the best defense against harmful CO build-up.

If a CO detector goes off, all occupants should be aware of the proper actions to take. If the alarm goes off and anyone experiences flu-like symptoms, all occupants should evacuate and alert the proper authorities. If the alarm goes off and all occupants are not experiencing symptoms, the building's doors and windows should be opened. The CO detector can then be reset. If elevated levels remain, the alarm may go off again. When CO is suspected, a qualified heating contractor should be contacted to inspect the location. Fuel-burning appliances should not be used until the area has been properly inspected. False alarms are possible, but it is important to respond as if all threats are real. The U.S. Consumer Product Safety Commission (CPSC) advises that homeowners request a professional inspection of all fuel-burning appliances to detect CO leaks.

Types of CO detectors: When selecting a CO detector, there are multiple types of alarm sensors to consider. While these sensors vary in cost, accuracy, and speed of response, they are all effective for about 3-5 years. Most models are not equipped with replaceable sensors. Consumers may also purchase wireless and/or hand-held CO detectors. These devices connect CO detectors to strobes, handsets, and vibrating pads. As such, people with various handicaps and illnesses, such as hearing or vision problems, will have extra time to evacuate if CO is present. The three types of CO detectors are: biomimetic sensors, electrochemical sensors, and semiconductor sensors.

Biomimetic (also known as chem-optical or gel cell) sensors use a synthetic form of hemoglobin. This protein, found in red blood cells, transports oxygen and carbon dioxide from the lungs to the body's tissues. When exposed to CO, the sensors darken; when CO leaves, the sensor lightens. Electrochemical sensors use fuel cells that produce a current precisely related to the amount of CO in the air. These are considered more accurate for detecting CO levels. They also require little electrical power and can last up to five years or more. Semiconductor sensors are comprised of thin wires on an insulating ceramic base. A current is generated that signals the alarm.

THEORY/EVIDENCE

CO poisoning: Without proper ventilation, carbon monoxide (CO) emissions can build up, resulting in the condition known as CO poisoning. As CO fumes are invisible, tasteless, and virtually odorless, people can inhale it without realizing it. A recent study published in Morbidity and Mortality Weekly Report found that the number of CO exposures and poisonings goes up in the fall and winter. This is because cooler weather generally requires increased use of gas furnaces, heaters, and generators in homes. Men were shown to be 2.3 times more likely to die from CO exposure than women. The reason for this may be because men, more often than women, typically take part in activities involving generators or power tools in enclosed spaces such as garages.

CO poisoning medical tests: When conducting CO poisoning tests, physicians measure the patient's levels of carboxyhemoglobin (COHb). The COHb test, the typical diagnostic test for CO poisoning, measures patients' COHb levels through whole blood or exhaled air. Hospital laboratories typically test and analyze blood with a device known as the multiple wavelength spectrophotometer (or "CO-oximeter"). This device measures a patient's heart rate, oxygen saturation, and COHb levels. Elevated COHb levels of 2% for non-smokers and between two and nine percent for smokers typically indicate a diagnosis of CO poisoning. With the COHb test, the amount of time since leaving the toxic environment is taken into account. This time away may impact patients' COHb levels. Breathing in non-polluted air for several hours may reduce the effectiveness of the COHb test.

The COHb test only measures CO contamination in a patient's blood. It does not measure the illness' severity, outcome, or how the patient will respond to therapy. That is why it is crucial for physicians to take account of any clinical symptoms and a history of exposure. This helps medical professionals determine the proper treatment type and intensity. Patients may require other tests, including an alcohol and toxicology screen, head CT scan, lumbar puncture, or fingerstick blood sugar test. These tests may be useful for determining altered mental status if CO poisoning cannot be proven. People afflicted with sickle cell disease often have elevated COHb levels. As such, physicians and healthcare professionals should be informed before they conduct a COHb test.

Treatment for CO poisoning: If patients are diagnosed with CO poisoning, physicians administer 100% pure oxygen until the symptoms are eliminated, which takes about 4-5 hours. Patients also receive periodic neurological exams to determine if CO levels are decreasing. These exams also detect if patients are at risk for cerebral edema, which is the swelling of the brain.

Hyperbaric oxygen therapy (HBO) therapy: Patients shown to have COHb levels of more than 25-30% are usually given hyperbaric oxygen therapy (HBO) therapy. First used in 1960, this involves the medical use of oxygen at higher-than-normal atmospheric pressure. A clinical review published in Toxicological Reviews showed that HBO therapy may eliminate CO accumulations in patients, while also reducing the incidence of further related health effects. Patients exposed to CO poisoning are usually given HBO therapy if they are 36 years or older. HBO therapy has been found to be safe and effective for treating CO poisoning in pregnant women for all levels of CO exposure. HBO therapy is also prescribed for patients demonstrating cardiovascular or neurological problems, short- or long-term unconsciousness, or severe acidosis (acidity of the blood).

Electrocardiogram (ECG, EKG): CO poisoning may have a dramatic effect on cardiovascular health. Studies show that if cardiac injuries occur during CO poisoning, the risk of death may increase for up to 10 years after the incident. For this reason, patients admitted to hospitals with severe CO poisoning should be given an electrocardiogram (ECG, EKG), which measures the heart's electrical activity over time. Physicians should also measure levels of cardiac enzymes and troponin, an essential mix of three proteins for muscle function.

X-rays, magnetic resonance imaging (MRI) scans, and computed tomography (CT, CAT) scans: Patients with very high levels of CO poisoning may be given chest X-rays. These are usually given if patients lose consciousness or display heart or lung problems. These patients may need magnetic resonance imaging (MRI) scans or computed tomography (CT, CAT) scans, which provide images of the internal body structures. MRI scans use large magnets and radio waves, while CT scans combine special X-ray equipment and sophisticated computers.

Follow-up medical exams: Following treatment for CO poisoning, discharged patients may be at risk for delayed neurological complications. These patients should be given comprehensive instructions. They should then return for follow-up medical and neurological exams within two weeks.

Environmental effects: CO is classified as one of six common air pollutants, known as "criteria pollutants." The other five criteria pollutants are particle pollution (PM), ground-level ozone, sulfur oxides, nitrogen oxides, and lead. With the passing of the Clean Air Act, the Environmental Protection Agency (EPA) was charged with monitoring the build-up of these pollutants. Studies illustrate that these air pollutants may cause serious damage to human and animal health, the environment, and structures and property. The EPA measures criteria pollutant levels by tracking outside air concentrations at selected American monitoring sites. The EPA also tracks the estimated emissions of the total tons of airborne pollutants annually.

While not considered a greenhouse gas, CO is necessary for the production of two harmful air pollutants: methane and tropospheric ozone. According to the National Oceanic and Atmospheric Administration (NOAA), the Northern Hemisphere contains about twice as much CO as the Southern Hemisphere. Research suggests that while CO levels were rising until the late 1980s, they have been declining since. This may be due to the increased use of catalytic converters, which reduce vehicle emissions. CO, along with sunlight, humidity, high temperatures, ozone, smoke, nitrogen, and hydrocarbons, combine to form smog. This murky, brown haze may cause serious breathing problems including decreased lung capacity, shortness of breath, pain when inhaling, wheezing, and coughing. Smog has also been shown to impair visibility, irritate the eyes and nose, and reduce the ability to fight infections.

Preventing or minimizing CO exposure: There are simple steps people can take to reduce or avoid CO build-up. It is important to make sure that homes, offices, schools, and other structures are properly ventilated. Combustion equipment should be properly maintained and adjusted, while gasoline-powered vehicles should not be used within confined spaces.

It is recommended that homeowners have trained professionals inspect, clean, and tune-up their central heating system every year. Gasoline-powered vehicles should be located away from living areas, garages, and other confined spaces. It is vital that people should see a physician or healthcare professional as soon as anyone feels dizzy, light-headed, or nauseous and CO poisoning is suspected.

CO detectors: Most leading healthcare and government agencies recommend that all U.S. homes install at least one carbon monoxide (CO) detector (also known as a CO alarm). A study published in The American Journal of Emergency Medicine showed that the louder a CO detector's alarm, the better the chance that occupants were alerted to potential CO poisoning. The occupants were also less likely to develop CO poisoning symptoms than those without detectors.

Historically, a different method was used for carbon monoxide testing. Throughout the 19th and even the 20th Centuries, American and British coal miners brought canaries into mines. As these birds have been shown to be more sensitive to the effects of CO and other toxic gases, they became sick first. If one of these canaries died in the coal mines, the miners would know to flee or take protective measures.

It is important to note that CO detectors are not the same as smoke detectors; smoke detectors only detect smoke particles, not CO. CO detectors are currently not fool-proof; their technology is still being improved. As of yet, these alarms are not considered as reliable as smoke detectors. Therefore, the removal of CO sources is still the best defense against harmful CO build-ups at home.

CO detectors are designed to warn occupants if pollutant levels accumulate to dangerous concentrations. These alarms test the air for CO every 1-3 minutes. These detectors should be equipped with loud alarms easily heard inside the home and garage. CO mixes freely with air, so detectors can be installed at any height. They should be installed away from smoke detectors, as the alarm sounds can overlap. CO alarms can utilize battery-power, a home's electrical system, or a standard 110V electrical outlet. Alarms should be tested regularly and be able to be reset easily. Battery-powered alarms should be tested weekly and the batteries should be replaced at least once a year. Hard-wired devices should be tested about once a month.

CO alarms may be unable to detect lower and possibly unhealthy CO concentrations, especially when the CO levels have been present in the nearby atmosphere for long periods of time. They can also fail to go off at high concentrations. When using CO detectors, it is best to ensure that there is proper ventilation, and all combustion devices are properly operated and maintained. CO detectors should be installed at least five feet away from household chemicals, as they can damage alarm sensors. Combustion devices may also interfere with CO detectors.

When a CO alarm goes off, all occupants should be aware of the proper actions to take. If the alarm goes off and any occupant experiences flu-like symptoms, everyone should evacuate and the proper authorities should be notified. If the alarm goes off, and all occupants are not experiencing symptoms, the structure's doors and windows should be opened. All fuel-burning appliances should be turned off. At this point, the CO detector can be reset. However, if elevated levels remain, alarms may go off again. When elevated CO levels are suspected, a qualified heating contractor should be contacted to inspect the location. Fuel-burning appliances should not be used until the area has been properly inspected. While false alarms are possible, it is important to respond as if the threat is real. The U.S. Consumer Product Safety Commission (CPSC) advises that homeowners request a professional inspection of all fuel-burning appliances to detect CO leaks.

HEALTH IMPACT/SAFETY

CO poisoning: Without proper ventilation, CO emissions can build up, resulting in the condition known as carbon monoxide (CO) poisoning. As these fumes are invisible, tasteless, and virtually odorless, they can be unknowingly inhaled. Effects of CO poisoning can vary greatly from person to person, depending on the person's age and overall health, as well as the concentration and length of exposure. CO fumes are considered very harmful to the health of humans and animals, as well as the environment.

Fetuses, infants, and people with cardiovascular or respiratory problems are particularly susceptible. Carbon monoxide poisoning may be especially dangerous for pregnant women. Exposure may increase short-term complication rates for expectant mothers. There may also be the risk of fetal death, developmental disorders, and chronic cerebral lesions.

CO exposure may lead to multiple health conditions, depending on the level of exposure. At lower concentrations, CO and flu symptoms may seem similar. Symptoms may include chest pain, confusion, headache, dizziness, weakness, and nausea and vomiting. In most cases, these symptoms go away after leaving the location of the CO emission. Higher levels of CO exposure may result in similar symptoms, as well as more serious conditions. Among these are impaired vision and coordination, cardiovascular, neurological, and respiratory problems, loss of consciousness, and death.

Multiple studies show that individuals with certain jobs and careers may be at greater risk for CO poisoning. Among these are coal miners, farmers, firefighters, utility workers, construction workers, hotel workers, and those employed in the fishing and forestry industries.

Cardiovascular effects: With CO poisoning, the body's red blood cells pick up CO faster than oxygen. This is because a compound known as carboxyhemoglobin (COHb) develops in the blood. COHb is a form of the protein hemoglobin, which is found in red blood cells. Hemoglobin transports oxygen and carbon dioxide between the lungs and body tissues. However, COHb interferes with the uses and functions of oxygen in the blood, including its transport and delivery to the body's tissues. As a result, blood rich in CO can prevent oxygen from being absorbed. Oxygen is then blocked from getting into the body. This reduces the amount of oxygen delivered to the body's organs, such as the heart and brain. These depleted oxygen levels can damage tissues and may result in death.

A study published in the Journal of Toxicology - Clinical Toxicology suggested that CO poisoning may be associated with multiple cardiovascular conditions. These include arrhythmia (an irregular heartbeat) and myocardial ischemia (reduced blood supply to the heart). Lower levels of CO exposure may be very harmful to people afflicted with conditions associated with heart disease, such as clogged arteries, congestive heart failure, and angina (tightness of the chest).

Heart injuries that occur during CO poisoning have been shown to increase the risk of death by up to 10 years after the incident. Patients admitted to hospitals with severe CO poisoning are given an electrocardiogram (ECG, EKG); this measures the heart's electrical activity over time. Physicians should also measure levels of cardiac enzymes and troponin, an essential mix of three proteins for muscle function. Studies show that higher levels may indicate cardiac damage caused by CO poisoning. Recent studies have found that for people suffering from heart disease, even one case of CO exposure may result in chest pain and a reduced ability to exercise. Additional exposures may contribute to a variety of cardiovascular problems.

Research shows that people afflicted with sickle cell disease, a blood disorder that results in abnormal red blood cells, often display elevated COHb levels. This is because patients with sickle cell may have elevated COHb levels, due to the condition known as hemolytic anemia (or hemolysis). This causes red blood cells to break open, releasing hemoglobin into the surrounding fluids. As such, physicians and healthcare professionals should be informed if patients have sickle cell disease before they receive a COHb test.

Neurological/CNS effects: Research shows that CO poisoning may lead to multiple neurological effects, such as disorientation, confusion, and coma. A study published in Toxicology suggested that CO exposure may lead to the development of delayed neuropsychiatric impairment. Neuropsychiatric impairment refers to mental disorders associated with the nervous system. Typically, these effects develop from two to 28 days after CO poisoning occurs. CO poisoning has been associated with reduced manual dexterity and difficulty in performing complex tasks. Following treatment for CO poisoning, discharged patients should be given comprehensive instructions and they return for a follow-up medical and neurological exam within two weeks.

Skin effects: Research shows that CO poisoning may lead to skin-related problems. Specifically, CO exposure has been linked with the development of skin lesions (rashes). CO poisoning may also cause the condition known as cyanosis. This involves the skin turning blue, due to decreased oxygen levels.

Eye and ear effects: Studies show that CO exposure may cause vision-related problems, such as blurry vision and double vision. CO may also cause agnosia, the inability to recognize and identify objects or persons. In addition, CO contributes to the formation of smog, which can irritate vision. Research suggests that CO poisoning may be associated with the loss of sensorineural hearing. This is hearing loss affecting the nerves responsible for transmitting sound and equilibrium (balance) information from the inner ear or brain. CO poisoning may also result in tinnitus, which is a buzzing or ringing sensation in the ear.

Breathing effects: A growing number of studies show that exposure to CO and other toxic air pollutants may be linked to increased occurrence of asthma. Asthma is a chronic, inflammatory lung disease in which the air passages within the lungs are constantly swollen, thus restricting the amount of air allowed to pass through the trachea. Asthmatics have recurrent breathing problems and a tendency to cough and wheeze. The American Lung Association estimates that about 20 million Americans have asthma, which causes about 5,000 deaths each year. CO poisoning may hold other risks for respiratory and pulmonary (lung) health, including rapid breathing and shortness of breath.

Patients with very high levels of CO poisoning may be given chest X-rays. These are usually given if patients lose consciousness or display heart or lung problems. CO poisoning may require the use of magnetic resonance imaging (MRI) scans or computed tomography (CT, CAT) scans, two non-invasive methods for exploring the inside of the body. MRI scans utilize large magnets and radio waves, while CT scans combine special

FUTURE RESEARCH OR APPLICATIONS

Research shows that efforts to limit and eliminate carbon monoxide poisoning may be working. Prior to the late 1980s, CO levels were found to be steadily rising. Since that time, CO levels have decreased. This is likely due to the increased use of catalytic converters, which have been shown to reduce vehicle emissions. Increased vehicle emission control systems have been very successful in reducing air pollution. But these benefits are offset by malfunctioning systems and vehicle tampering.

The exhaust from motor vehicles represents a pollution problem. It is estimated that they make up about 56% of the nation's CO emissions, while non-road engines and vehicles, including boats and construction equipment, make up an additional 22%. However, this trend may not last as more and more vehicles are being driven throughout the nation and the world. Over the past 20 years, it is estimated that the number of vehicles on the road and the miles they are driven has doubled. As such, this explosive growth may erase any progress gained from tight vehicle emission controls.

In the early 1970s, the Environmental Protection Agency (EPA) set national standards for reducing motor vehicles' emissions of CO and other pollutants. Since 1970, CO emissions from "on-road" vehicles, such as cars, motorcycles, and light- and heavy-duty trucks, have been reduced by over 40%; car emissions alone have been reduced by almost 60%.

The EPA, along with state and local governments, is striving to reduce CO emissions. The agency's main approach has been the establishment of national ambient air quality standards. This program requires national controls for motor vehicle emissions and reductions from large industrial facilities. The EPA has established two national health protection standards for CO. The first calls for a one-hour standard of 35 parts per million (ppm) and an eight-hour standard of 9ppm. The other calls for nationwide air quality stations that measure levels of CO and other air pollutants. Additionally, the EPA requires large industrial or commercial facilities to obtain permits prior to construction. This ensures that the facilities, especially their boilers and incinerators, are well-controlled and do not cause serious health and environmental damage.

CO is one of six toxic air pollutants known as "criteria pollutants." The other five are particle pollution (PM), ground-level ozone, sulfur oxides, nitrogen oxides, and lead. These air pollutants may cause serious damage to human and animal health, the environment, and structures and property. With the passing of the Clean Air Act, the Environmental Protection Agency (EPA) was charged with monitoring the build-up of these air pollutants. The EPA measures the levels of the pollutants in two ways. It tracks outside air concentrations at selected American monitoring sites. The EPA also tracks the estimated emissions of the total tons of airborne pollutants annually.

CO detectors: Carbon monoxide detectors (or CO alarms) are designed to warn occupants if pollutant levels accumulate to dangerous concentrations. While these sensors vary in cost, accuracy, and speed of response, they all typically last for about three to five years. Most models are not equipped with replaceable sensors. As of yet, CO detectors are still not considered as reliable as smoke detectors. CO detectors are usually unable to sense lower and possibly unhealthy, CO concentrations, especially when the CO levels have been present in the nearby atmosphere for long periods of time. Their alarms can also fail to go off at high CO concentrations. Therefore, removing CO sources is still the best way to ensure that homes and offices are safe.

AUTHOR INFORMATION

This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

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