In the last several years, a growing body of scientific evidence has indicated that the air within homes and other buildings can be more seriously polluted than the outdoor air in even the largest and most industrialized cities. Other research indicates that people spend approximately 90% of their time indoors. Thus, for many people, the risks to health from exposure to indoor air pollution may be greater than risks from outdoor pollution.
Toxics and Irritants. Many molds also produce mycotoxins that can be a health hazard on ingestion, dermal contact, or inhalation [14]. Although common outdoor molds present in ambient air, such as Cladosporium cladosporioides and Alternaria alternata, do not usually produce toxins, many other different mold species do [17]. Genera-producing fungi associated with wet buildings, such as Aspergillus versicolor, Fusarium verticillioides, Penicillium aiurantiorisen, and S. chartarum, can produce potent toxins [17]. A single mold species may produce several different toxins, and a given mycotoxin may be produced by more than one species of fungi. Furthermore, toxin-producing fungi do not necessarily produce mycotoxins under all growth conditions, with production being dependent on the substrate it is metabolizing, temperature, water content, and humidity [17]. Because species of toxin-producing molds generally have a higher water requirement than do common household molds, they tend to thrive only under conditions of chronic and severe water damage [18]. For example, Stachybotrys typically only grows under continuously wet conditions [19]. It has been suggested that very young children may be especially vulnerable to certain mycotoxins [19, 20]. For example, associations have been reported for pulmonary hemorrhage (bleeding lung) deaths in infants and the presence of S. chartarum [21,22,23, 24]. Causes of Mold. Mold growth can be caused by any condition resulting in excess moisture. Common moisture sources include rain leaks (e.g., on roofs and wall joints); surface and groundwater leaks (e.g., poorly designed or clogged rain gutters and footing drains, basement leaks); plumbing leaks; and stagnant water in appliances (e.g., dehumidifiers, dishwashers, refrigerator drip pans, and condensing coils and drip pans in HVAC systems). Moisture problems can also be due to water vapor migration and condensation problems, including uneven indoor temperatures, poor air circulation, soil air entry into basements, contact of humid unconditioned air with cooled interior surfaces, and poor insulation on indoor chilled surfaces (e.g., chilled water lines). Problems can also be caused by the production of excess moisture within homes from humidifiers, unvented clothes dryers, overcrowding, etc. Finished basements are particularly susceptible to mold problems caused by the combination of poorly controlled moisture and mold-supporting materials (e.g., carpet, paper-backed sheetrock) [15]. There is also some evidence that mold spores from damp or wet crawl spaces can be transported through air currents into the upper living quarters. Older, substandard housing low income families can be particularly prone to mold problems because of inadequate maintenance (e.g., inoperable gutters, basement and roof leaks), overcrowding, inadequate insulation, lack of air conditioning, and poor heating. Low interior temperatures (e.g., when one or two rooms are left unheated) result in an increase in the relative humidity, increasing the potential for water to condense on cold surfaces.
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Removal and Cleaning of Mold-contaminated Materials. Nonporous (e.g., metals, glass, and hard plastics) and semiporous (e.g., wood and concrete) materials contaminated with mold and that are still structurally sound can often be cleaned with bleach-and-water solutions. However, in some cases, the material may not be easily cleaned or may be so severely contaminated that it may have to be removed. It is recommended that porous materials (e.g., ceiling tiles, wallboards, and fabrics) that cannot be cleaned be removed and discarded [29]. In severe cases, clean-up and repair of mold-contaminated buildings may be conducted using methods similar to those used for abatement of other hazardous substances such as asbestos [30]. For example, in situations of extensive colonization (large surface areas greater than 100 square feet or where the material is severely degraded), extreme precautions may be required, including full containment (complete isolation of work area) with critical barriers (airlock and decontamination room) and negative pressurization, personnel trained to handle hazardous wastes, and the use of full-face respirators with HEPA filters, eye protection, and disposable full-body covering [26].
Reducing and controlling lead hazards can be successfully accomplished without destroying the character-defining features and finishes of historic buildings. Federal and state laws generally support the reasonable control of lead-based paint hazards through a variety of treatments, ranging from modified maintenance to selective substrate removal. The key to protecting children, workers, and the environment is to be informed about the hazards of lead, to control exposure to lead dust and lead in soil and lead paint chips, and to follow existing regulations.
Complaints are often raised when construction activities are carried out in a densely-populated area or near vibration-sensitive facilities. Early phases of construction projects often generate vibrations in the near-surface soils. These construction activities can include the removal of existing bridges, buildings, or hardscape. The activities can also include soil excavation, pile driving, site clearing, truck traffic, or compaction with vibratory equipment.
Site clearing includes the removal of existing vegetation, buildings, and pavement. This process is often performed with vibration-inducing equipment such as excavators, dozers, loaders, and large trucks. Additionally, even explosives are used in some cases with the demolition of large structures.
Vibration is typically used in soil compaction equipment because it improves the efficiency of the equipment by directing energy into the substrate which overcomes the friction between soil particles, causing the soil particles to re-align and fill in the void spaces, thus resulting in greater soil density and preventing excessive building settlement. When vibratory equipment is used, it results in improved density in less time and effort and increases the depth of penetration of the compaction equipment. In other words, the higher the mechanical energy that a machine delivers into the soils, the better and faster the compaction. While use of vibratory equipment has its obvious advantages in construction, it can also create adverse effects on adjacent buildings, facilities, and people. If proper precautions are not taken, site compaction methods can be at opposition with neighboring building occupants.
For larger buildings, buildings constructed on poor soil, or buildings constructed near open water, oftentimes a deep foundation system is required to support the building. Concrete, steel, and timber piles are the most common types of deep foundations, and they are installed by driving them into the ground with a large hammer, or by vibratory methods. Both installation methods will generate large vibrations which can be an annoyance to and/or damage adjacent properties.
The building components can vary from flexible, such as wood and steel, to rigid, such as masonry and concrete. These components are then typically covered with decorative and cosmetic finishes. Damage resulting from vibrations will affect flexible components at connections, which are the most rigid portions of a flexible assembly. Conversely, damage to rigid components will appear as cracks or post-construction differential settlement. Rigid components will generally be affected by vibrational forces before flexible components.
For example, on roadway projects in the state of Florida, the Florida Department of Transportation requires vibration monitoring on nearby structures. Based on Chapter 108-2 of the FDOT Standard Specifications for Road and Bridge Construction, during construction of retaining walls and foundations for bridges, buildings, and structures, all nearby structures within 200 feet of sheet pile installation/extraction, and within 100 feet of soldier pile installation/extraction must be inspected, surveyed, and monitored for settlement. In addition, when performing roadway compaction operations, all nearby structures within 75 feet of vibratory compaction operations must be surveyed and monitored for settlement.
A pre-construction survey should document the condition of the structure and all existing cracks in order to determine whether any new cracks appeared during construction. Vibration levels can be monitored during construction with a seismograph to determine if the vibration levels exceeded the building damage threshold. However, many times, vibration monitoring is not performed, and pre- and post-construction surveys are not available. Therefore, vibration analyses can be performed to estimate the vibration levels which would have been present at the property and compare them to the minimum vibration level required to damage a structure. According to Florida Statute 552.30, direct ground vibrations generated by construction mining activities are limited to the maximum standards set by the United States Bureau of Mines Report of Investigation No. 8507 (1980). While these regulations specifically apply to mining, they are commonly applied to construction operations. 2ff7e9595c
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