Particulates
Environmental tobacco smoke, ETS (smoke that nonsmokers are exposed to from smokers), has been judged by the Surgeon General, the National Research Council, and the International Agency for Research on Cancer to pose a risk of lung cancer to nonsmokers. Nonsmokers’ exposure to ETS is called “passive smoking,” “second-hand smoking,” and “involuntary smoking.” Tobacco smoke contains a number of pollutants, including inorganic gases, heavy metals, particulates, VOCs, and products of incomplete burning, such as polynuclear aromatic hydrocarbons. Smoke can also yield a number of organic compounds. Including both gases and particles, tobacco smoke is a complex mixture of over 4700 compounds [I].
There are two components of tobacco smoke: [1] [2]
Studies indicate that exposure to tobacco smoke may increase the risk of lung cancer by an average of 30% in the nonsmoking spouses of smokers. Published risk estimates of lung cancer deaths among nonsmokers exposed to tobacco smoke conclude that ETS is responsible for 3000 deaths each year [5]. It also seriously affects the respiratory health of hundreds of thousands of children. Very young children exposed to smoking at home are more likely to be hospitalized for bronchitis and pneumonia. Recent studies suggest that ETS can also cause other diseases, including other cancers and heart disease in healthy nonsmokers [1].
The best way to reduce exposure to cigarette smoke in the house is to quit smoking and discourage smoking indoors. Ventilation is the most common method of reducing exposure to these pollutants, but it will not eliminate it altogether. Smoking produces such large amounts of pollutants that neither natural nor mechanical methods can remove them from the air as quickly as they build up. In addition, ventilation practices sometimes lead to increased energy costs.
RSP are particles or fibers in the air that are small enough to be inhaled. Particles can exist in either solid or liquid phase or in a combination. Where these particles are deposited and how long they are retained depends on their size, chemical composition, and density. RSP (generally less than 10 pm in diameter) can settle on the tissues of the upper respiratory tract, with the smallest particles (those less than 2.5 pm) penetrating the alveoli, the small air sacs in the lungs.
Particulate matter is a broad class of chemically and physically diverse substances that present risks to health. These effects can be attributed to either the intrinsic toxic chemical or physical characteristics, as in the case of lead and asbestos, or to the particles acting as a carrier of adsorbed toxic substances, as in the case of attachment of radon daughters. Carbon particles, such as those created by combustion processes, are efficient adsorbers of many organic compounds and are able to carry toxic gases such as sulfur dioxide into the lungs.
Asbestos is a mineral fiber used mostly before the mid-1970s in a variety of construction materials. Home exposure to asbestos is usually due to aging, cracking, or physical disruption of insulated pipes or asbestos-containing ceiling tiles and spackling compounds. Apartments and school buildings may have an asbestos compound sprayed on certain structural components as a fire retardant. Exposure occurs when asbestos materials are disturbed and the fibers are released into the air and inhaled. Consumer exposure to asbestos has been reduced considerably since the mid-1970s, w'hen use of asbestos was either prohibited or stopped voluntarily in sprayed-on insulation, fire protection, soundproofing, artificial logs, patching compounds, and handheld hair dryers. Today, asbestos is most commonly found in older homes in pipe and furnace insulation materials, asbestos shingles, millboard, textured paints and other coating materials, and floor tiles. Elevated concentrations of airborne asbestos can occur after asbestos-containing materials are disturbed by cutting, sanding, or other remodeling activities. Improper attempts to remove these materials can release asbestos fibers into the air in homes, thereby increasing asbestos levels and endangering the people living in those homes. The most dangerous asbestos fibers are too small to be visible. After they are inhaled, they can remain and accumulate in the lungs. Asbestos can cause lung cancer, mesothelioma (a cancer of the chest and abdominal linings), and asbestosis (irreversible lung scarring that can be fatal). Symptoms of these diseases do not show up until many years after exposure began. A more detailed presentation on asbestos can be found in Part IV, Chapter 28.
Lead has long been recognized as a harmful environmental pollutant. There are many ways in which humans are exposed to lead, including air, drinking water, food, and contaminated soil and dust. Airborne lead enters the body w'hen an individual breathes lead particles or swallows lead dust once it has settled. Until recently, the most important airborne source of lead was automobile exhaust. Lead-based paint has long been recognized as a hazard to children who eat lead- contained paint chips. A 1988 National Institute of Building Sciences Task Force report found that harmful exposures to lead can be created when lead-based paint is removed from surfaces by sanding or open-flame burning. High concentrations of airborne lead panicles in homes can also result from the lead dust from outdoor sources, contaminated soil tracked inside, and use of lead in activities such as soldering, electronics repair, and stained-glass artwork. Lead is toxic to many organs within the body at both low and high concentrations. Lead is capable of causing serious damage to the brain, kidneys, peripheral nervous system (the sense organs and nerves controlling the body), and red blood cells. Even low levels of lead may increase high blood pressure in adults. Fetuses, infants, and children are more vulnerable to lead exposure than are adults because lead is more easily absorbed into growing bodies, and the tissues of small children are more sensitive to the damaging effects of lead. The effects of lead exposure on fetuses and young children include delays in physical and mental development, lower IQ levels, shortened attention spans, and increased behavioral problems. Additional details on lead, as well as other metals, are available in Part IV, Chapter 29.
Particles present a risk to health out of proportion to their concentration in the atmosphere because they deliver a high-concentration package of potentially harmful substances. So, while few cells may be affected at any one time, those few that are can be badly damaged. Whereas larger particles deposited in the upper respiratory portion of the respiratory system are continuously cleared away, smaller particles deposited deep in the lung may cause adverse health effects. Particle sizes vary over a broad range, depending on source characteristics.
Major effects of concern attributed to particle exposure are impairment of respiratory mechanics, aggravation of existing respiratory and cardiovascular disease, and reduction in particle clearance and other host defense mechanisms. Respiratory effects can range from mild transient changes of little direct health significance to incapacitating impairment of breathing.
One method of reducing RSP concentrations is to properly design, install, and operate combustion sources. One should make sure there are no existing leaks or cracks in stovepipes, and that these appliances are always vented to the outdoors.
Also available are particulate air cleaners, which can be separated into mechanical filters and electrostatic filters. Mechanical filtration is generally accomplished by passing the air through a fibrous media (wire, hemp, glass, etc.). These filters are capable of removing almost any sized particles. Electrostatic filtration operates on the principle of attraction between opposite electrical charges. Ion generators, electrostatic precipitators, and electric filters use this principle for removing particles from the air.
The ability of these various types of air-cleaning devices to remove respirable particles varies widely. High-efficiency particulate air (HEPA) filters can capture over 99% of particles and are advantageous in that filters only need changing every 3-5 years, but costs can reach $500-$800. It is also important to note the location of air-cleaning device inlets in relation to the contaminant sources as an important factor influencing removal efficiencies.
