INDOORAIRQUALITYINCOMMERCIALANDINSTITUTIONALBUILDINGS13Carbondioxide.docx
I N D O O R A I R Q U A L I T Y I N C O M M E R C I A L A N D I N S T I T U T I O N A L B U I L D I N G S 1 3 Carbon dioxide (CO2) CO2 is a colorless, odorless, and tasteless gas (36). It is a product of completed carbon combustion and the by-product of biological respiration. ASHRAE states that CO2 concentrations in acceptable outdoor air typically range from 300-500 ppm. Adverse health effects from CO2 may occur since it is an asphyxiant gas. At concentrations above 15,000 ppm, some loss of mental acuity has been noted (36). The OSHA PEL is 5,000 ppm as an 8-hour TWA. The CO2 levels can be used as a rough indicator of the effectiveness of ventilation (26), and excessive population density in a structure. CO2 increases in buildings with higher occupant densities, and is diluted and removed from buildings based on outdoor air ventilation rates. Therefore, examining levels of CO2 in indoor air can reveal information regarding occupant densities and outdoor air ventilation rates. High CO2 levels may indicate a problem with overcrowding or inadequate outdoor air ventilation rates. Carbon Dioxide Poisoning – Symptoms CO2, a by-product of normal cell function, is removed from the body via the lungs in the exhaled air. Exposure to high levels of CO2 can increase the amount of this gas in the blood, which is referred to as hypercapnia or hypercarbia. As the severity of hypercapnia increases, more symptoms ranging from headache to unconsciousness appear, and it can also lead to death (36, 37). Pesticides Pesticides are any substances or mixture of substances used for preventing, destroying, repelling, or mitigating any pest. These substances include insecticides, herbicides, fungicides, and various other substances used to control pests. Pesticides can cause harm to humans, animals, and the environment because they are designed to kill or otherwise adversely affect living organisms. Pesticides can also kill potential disease-causing organisms (8, 38). Pesticide Poisoning Symptoms Symptoms of pesticide poisoning depend heavily on the pesticide to which the worker was exposed. Symptoms often appear within minutes of pesticide exposure, but may take much longer to develop. The most common symptoms include headache, tears in the eyes, vomiting, sweating, and general weakness. Exposure to high doses may cause seizures and death. Appendix A: Common Indoor Air Contaminants The purpose of this section is to provide additional information about several common indoor air contaminants. Carbon monoxide (CO) CO is a colorless, odorless gas produced by the incomplete burning of material containing carbon. CO poisoning2 can cause brain damage and death. Common sources of CO are leaking vented combustion appliances, automobile exhaust, parking garages, etc. When not properly ventilated, emitted CO can build up. Employees exposed to low levels of CO may feel sick with headache and nausea, and will feel better when exposed to fresh air outside. However, their symptoms will recur shortly after returning to their workplace if CO is not eliminated. CO Poisoning Symptoms Poisoning due to low levels of CO can be confused with influenza symptoms, food poisoning, or other illnesses, and can be a long-term health risk if left unattended. Some of the symptoms of low-level CO poisoning are shortness of breath, mild nausea, and mild headaches (30-35). Prolonged exposure to high levels of CO can lead to brain damage and even death. Adequate ventilation is an important control measure. The OSHA Permissible Exposure Limit (PEL) for CO is 50 parts per million (ppm) as an 8-hour time-weighted average (TWA); the National Institute for Occupational Safety and Health has a Recommended Exposure Limit (REL) of 35 ppm as a 10-hour TWA. According to the American Conference of Governmental Industrial Hygienists (ACGIH), the threshold limit value for CO is 25 ppm as an 8-hour TWA. Carbon Monoxide Detectors In addition to having a professional inspect appliances and furnaces, commercially available carbon monoxide detectors can be used to monitor the levels of carbon monoxide in buildings throughout the year. The manufacturer’s instructions on placement and maintenance should be followed. 1 4 Occupational Safety and Health Administration 2CO is a chemical asphyxiant; it displaces O2 in the blood, thereby suffocating the person exposed. Small dust particles may remain airborne for long periods, while large particles settle more quickly. However, particles that have settled may be easily resuspended in the ambient air by currents of air or other disturbances. Drapery, carpet and other places where dust collects can harbor these contaminants; dirty cooling coils, humidifiers, condensate drains, and ductwork can incubate bacteria and molds. Areas with high humidity can accelerate their growth. The most common sources of biological air contaminants are moisture-laden areas that support the growth of mold and bacteria present in the air (8, 16, 19, 44). Also, wet surfaces can provide a breeding ground for insects such as dust mites. Moisture-induced microbial growth can result from water leaks and/or by condensation due to high humidity. Persistent dampness and microbial growth on interior surfaces and in building structures should be avoided or minimized as they may lead to adverse health effects (15). Common sources of moisture in buildings include: plumbing; roof and window leaks; flooding; condensation on cold surfaces, e.g., pipe sweating; poorly maintained drain pans; and wet foundations caused by landscaping or gutters that direct water into or under the building. Water vapor from unvented or poorly vented kitchens, showers, combustion appliances, or steam pipes can also create conditions that promote microbial growth. The most effective means to prevent or minimize adverse health effects is to determine the sources of persistent dampness in the workplace and eliminate them. Also, strict adherence to a housekeeping schedule and use of HEPA-filtered vacuum cleaners will help reduce ambient levels of allergens. Damp Indoor Environments Damp indoor environments have been associated with many serious health effects, including asthma, hypersensitivity, and sinusitis. Moisture incursion leading to dampness can result from water leaks and/or by condensation due to high humidity. Common sources of moisture in buildings include: plumbing; roof and window leaks; flooding; condensation on cold surfaces, e.g., pipe sweating; poorly-maintained drain pans; and wet foundations due to landscaping or gutters that direct water into or under the building. Water vapor from unvented or poorly-vented kitchens, showers, combustion appliances, or steam pipes can also create conditions that promote microbial growth. Steps to Reduce Exposure Integrated Pest Management Principles should always be implemented. Pesticide products should be used according to application and ventilation instructions provided by the manufacturer. In addition: • Mix or dilute pesticides outdoors; • Increase ventilation when using pesticides; • Use non-chemical methods of pest control when possible; • Do not store unneeded pesticides; • Dispose of unwanted containers safely; and • Keep indoor spaces clean, dry, and well ventilated to avoid pest problems. Radon Radon is a colorless, odorless, and tasteless radioactive gas (6, 13, 17, 39, 40). It comes from the natural decay of uranium and some other radionuclides that are present in soil. Radon is responsible for most of the public’s exposure to ionizing radiation (39, 40). It is often the single largest contributor to an individual's background radiation dose, and levels can vary widely from location to location. Radon gas can accumulate in buildings, especially in confined areas such as attics and basements. Radon penetrates cracks and drain openings in foundations, basements, and crawl spaces. Some building materials will also release radon into the air. It can also be found in some spring waters and hot springs, where it can be released into the air when the water is drawn for use indoors. Exposure to radon may cause lung cancer in humans. The EPA recommends taking actions to reduce radon exposure if levels exceed four picocuries per liter of air (4 pCi/L) (25). Active soil depressurization and building ventilation are the two most commonly used strategies for controlling radon in buildings. Radon reduction methods include sealing concrete slab floors, basement foundations, and water drainage systems, and increasing ventilation. These techniques are usually cost-effective, and can greatly reduce or eliminate contamination and the associated health risks. Biological Contaminants Animals, plants, and microbes are sources of air pollutants. Dander from animals, pollens from plants, and microbes, may act as allergens when they are inhaled. These biological contaminants are usually attached to dust particles of various sizes. I N D O O R A I R Q U A L I T Y I N C O M M E R C I A L A N D I N S T I T U T I O N A L B U I L D I N G S 1 5 Volatile Organic Compounds (VOCs) VOCs refer to organic chemical compounds that have significant vapor pressures, and that can adversely affect the environment and human health. VOCs are emitted as vapors from certain solids or liquids, and include a variety of chemicals, some of which may have short- and long-term adverse health effects (17, 45, 46). Concentrations of many VOCs are consistently higher indoors (up to ten times higher) than outdoors. VOCs are emitted by a wide array of products numbering in the thousands. Examples include paints and lacquers, paint strippers, cleaning supplies, pesticides, building materials and furnishings, office equipment such as copiers and printers, correction fluids and carbonless copy paper, and graphics and craft materials, including glues and adhesives, permanent markers, and photographic solutions (8). More commonly known VOCs include benzene, formaldehyde, methylene chloride, trichloroethylene, and tetrachloroethylene (13). Exposure to VOCs can result in both acute and chronic health effects, depending on many factors such as the level of exposure and the length of exposure. A few VOCs, such as benzene, have been directly linked to cancer in humans, and others are suspected of causing cancer. Since people today spend most of their time at home or in an office, long-term exposure to VOCs in the indoor environment can contribute to IAQ related problems (31). In offices, VOCs result from new furnishings, wall coverings, and office equipment such as photocopy machines, which can offgas VOCs into the air (47, 48). Good ventilation and air-conditioning systems are essential to reduce VOC emissions in the indoor environment (47). Steps to Reduce Exposure (http://www.epa.gov/iaq/voc.html) • Use products according to manufacturer’s directions. • Make sure that plenty of fresh air is provided when using these products. • Discard used containers safely. • Buy quantities that can be used in short periods of time. Well-designed, -constructed and –maintained building envelopes are critical to the prevention and control of excess moisture and microbial growth by avoiding thermal bridges and preventing intrusion by liquid or vapor-phase water. Management of moisture requires proper control of temperatures and ventilation to avoid high humidity, condensation on surfaces, and excess moisture in materials. Ventilation should be distributed effectively in spaces, and stagnant air zones should be avoided (5, 8). ASHRAE recommends relative humidity levels between 30 and 60 percent for optimum comfort (25). Higher humidity may result in microbial growth. A consistently implemented good-housekeeping plan is essential to eliminate or reduce the microbial growth in the building. Legionella Legionellosis or Legionnaires’ Disease is caused by a waterborne bacterium, Legionella, which grows best in slow-moving, or still warm water (42-44). The primary route of exposure is aerosolization, most commonly from domestic hot-water systems (e.g., showers, sprays, etc.). Mist from evaporative cooling towers without biocide treatment is another reported source. Outbreaks in medical facilities can occur because the patients often have weak or suppressed immune systems. For cooling towers and evaporative condensers, prevention efforts center on improving the location and maintenance of the cooling towers to limit the growth and spread of Legionella bacteria. These devices should be inspected and thoroughly cleaned at least once a year. Corroded parts, such as drift eliminators, should be replaced, and algae and accumulated scale should be removed. Cooling water should be treated constantly with antimicrobial agents. Ideally, an automatic water-treatment system should be used that continuously controls the quality of the circulating water. For domestic hot-water systems, prevention efforts focus on controlling water temperature, avoiding dead-legs, avoiding stagnation, and cleaning storage tanks to limit the growth and spread of Legionella bacteria. 1 6 Occupational Safety and Health Administration Appendix B: Steps to Improve Indoor Air Quality3 What employers can do • Maintain a good working relationship with building management on indoor environmental issues. • Place office furniture and equipment in locations based on the adequate air circulation, temperature control, and pollutant removal functions of the HVAC system. • Coordinate with building management when responsibility for design, operation, and maintenance of the ventilation system is shared. • Avoid procedures and products that can cause IAQ problems. • Integrate IAQ concerns into purchasing decisions. • Work with the building manager to ensure use of only necessary and appropriate pest-control practices; use nonchemical methods when possible. • Work with building management and the contractor before starting to remodel or renovate to identify ways of minimizing building-occupant exposure, and to ensure that the air-distribution system is not disrupted. • Encourage building management to develop a preventive IAQ management program following guidance issued by the EPA and the National Institute for Occupational Safety and Health. I N D O O R A I R Q U A L I T Y I N C O M M E R C I A L A N D I N S T I T U T I O N A L B U I L D I N G S 1 7 3See Item 29 in the last section of this document titled “References.” What workers can
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