Friday, July 31, 2009


Description of Silicosis

When workers inhale crystalline silica, the lung tissue reacts by developing fibrotic nodules and scarring around the trapped silica particles [Silicosis and Silicate Disease Committee 1988]. This fibrotic condition of the lung is called silicosis. If the nodules grow too large, breathing becomes difficult and death may result. Silicosis victims are also at high risk of developing active tuberculosis [Myers et al. 1973; Sherson and Lander 1990; Bailey et al. 1974].
A worker's lungs may react more severely to silica sand that has been freshly fractured (sawed, hammered, or treated in a way that produces airborne dust) [Vallyathan et al. 1988]. This factor may contribute to the development of acute and accelerated forms of silicosis.

Types of Silicosis

A worker may develop any of three types of silicosis, depending on the airborne concentration of crystalline silica:

  • Chronic silicosis, which usually occurs after 10 or more years of exposure to crystalline silica at relatively low concentrations
  • Accelerated silicosis, which results from exposure to high concentrations of crystalline silica and develops 5 to 10 years after the initial exposure
  • Acute silicosis, which occurs where exposure concentrations are the highest and can cause symptoms to develop within a few weeks to 4 or 5 years after the initial exposure [Peters 1986; Ziskind et al. 1976]

Initially, workers with silicosis may have no symptoms. As silicosis progresses, there may be difficulty in breathing and other chest symptoms such as cough. Infectious complications may cause fever, weight loss, and night sweats. Severe mycobacterial or fungal infections can complicate silicosis and may be fatal [Ziskind et al. 1976; Owens et al. 1988; Bailey et al. 1974]. Fungal or mycobacterial infections are believed to result when the lung cells (macrophages) that fight these infections are overwhelmed with silica dust and are unable to kill mycobacteria and other organisms [Allison and Hart 1968; Ng and Chan 1991]. About half of the mycobacterial infections are caused by Mycobacterium tuberculosis (TB), with the other half caused by M. kansasii and M. avium-intracellulare [Owens et al. 1988]. Nocardia and Cryptococcus may also cause infections in silicosis victims [Ziskind et al. 1976].

Medical evaluations of silicosis victims usually show the lungs to be filled with silica crystals and a protein material [Owens et al. 1988; Buechner and Ansari 1969]. Pulmonary fibrosis (fibrous tissue in the lung) may or may not develop in acute cases of silicosis, depending on the time between exposure and onset of symptoms.

Furthermore, evidence indicates that crystalline silica is a potential occupational carcinogen [NIOSH 1988; IARC 1987; DHHS 1991], and NIOSH is reviewing the data on carcinogenicity.


Thursday, July 30, 2009

Silica, Crystalline, Silicosis Safety Issues

Recognizing potential hazards is key in preventing and minimizing the effects of silica exposure. Silicosis is a disabling, nonreversible and sometimes fatal lung disease caused by overexposure to respirable crystalline silica. The following references aid in recognizing crystalline silica hazards and health effects.

What is crystalline silica?

Crystalline silica is a basic component of soil, sand, granite, and many other minerals. Quartz is the most common form of crystalline silica. Cristobalite and tridymite are two other forms of crystalline silica. All three forms may become respirable size particles when workers chip, cut, drill, or grind objects that contain crystalline silica.

What are the hazards of crystalline silica?

Silica exposure remains a serious threat to nearly 2 million U.S. workers, including more than 100,000 workers in high risk jobs such as abrasive blasting, foundry work, stonecutting, rock drilling, quarry work and tunneling. The seriousness of the health hazards associated with silica exposure is demonstrated by the fatalities and disabling illnesses that continue to occur in sandblasters and rockdrillers. Crystalline silica has been classified as a human lung carcinogen. Additionally, breathing crystalline silica dust can cause silicosis, which in severe cases can be disabling, or even fatal. The respirable silica dust enters the lungs and causes the formation of scar tissue, thus reducing the lungs’ ability to take in oxygen. There is no cure for silicosis. Since silicosis affects lung function, it makes one more susceptible to lung infections like tuberculosis. In addition, smoking causes lung damage and adds to the damage caused by breathing silica dust.


Friday, July 24, 2009

Healthy School Environments Assessment Tool (HealthySEAT)

HealthySEAT is a new software tool from EPA designed to help school districts conduct voluntary, customized self-assessments of their school facilities for environmental, health, and safety hazards.

More than 53 million children and about 6 million adults spend a significant portion of their days in more than 120,000 public and private school buildings. Many of these buildings are old and in poor condition, and may contain environmental conditions that inhibit learning and pose increased risks to the health of children and staff. The healthy school environments web site is designed to provide one-stop access to the many programs and resources available to help prevent and resolve environmental issues in schools.

For more information visit:

Source: EPA - Office of Air and Radiation - Indoor Environments Division

Thursday, July 23, 2009

Ten Things You Should Know About Mold per USEPA

As per the USEPA:
  1. Potential health effects and symptoms associated with mold exposures include allergic reactions, asthma, and other respiratory complaints.
  2. There is no practical way to eliminate all mold and mold spores in the indoor environment; the way to control indoor mold growth is to control moisture.
  3. If mold is a problem in your home or school, you must clean up the mold and eliminate sources of moisture.
  4. Fix the source of the water problem or leak to prevent mold growth.
  5. Reduce indoor humidity (to 30-60% ) to decrease mold growth by: venting bathrooms, dryers, and other moisture-generating sources to the outside; using air conditioners and de-humidifiers; increasing ventilation; and using exhaust fans whenever cooking, dishwashing, and cleaning.
  6. Clean and dry any damp or wet building materials and furnishings within 24-48 hours to prevent mold growth.
  7. Clean mold off hard surfaces with water and detergent, and dry completely. Absorbent materials such as ceiling tiles, that are moldy, may need to be replaced.
  8. Prevent condensation: Reduce the potential for condensation on cold surfaces (i.e., windows, piping, exterior walls, roof, or floors) by adding insulation.
  9. In areas where there is a perpetual moisture problem, do not install carpeting (i.e., by drinking fountains, by classroom sinks, or on concrete floors with leaks or frequent condensation).
  10. Molds can be found almost anywhere; they can grow on virtually any substance, providing moisture is present. There are molds that can grow on wood, paper, carpet, and foods.


Tuesday, July 21, 2009

Cleaning and Remediation of Flood Contaminated HVAC Systems

As per NIOSH Interim Recommendations for the Cleaning and Remediation of Flood-Contaminated HVAC Systems: A Guide for Building Owners and Managers

During flooding, systems for heating, ventilating, and air conditioning (HVAC) can become submerged in flood waters. As a result, these systems may contain substantial amounts of dirt and debris and may also become contaminated with various types of microorganisms such as bacteria and fungi. The following recommendations will help ensure that HVAC systems contaminated with flood water are properly cleaned and remediated to provide healthy indoor environments.

Microorganisms may grow on all surfaces of HVAC system components that weresubmerged in flood waters. In addition, moisture can collect in HVAC systemcomponents that were not submerged (such as air supply ducts above the water line)and can promote the growth of microorganisms. Therefore, all components of the HVACsystem that were contaminated with flood water or moisture should be thoroughlyinspected, cleaned of dirt and debris, and disinfected by a qualified professional. Thefollowing recommendations will help ensure that HVAC systems contaminated withflood water are properly cleaned and remediated to provide healthy indoorenvironments.

These interim recommendations are based on current knowledge as ofSeptember 21, 2005; the recommendations will be updated and revised as appropriate,as additional information becomes available.

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