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Health Effects of Particulate Matter and Silica Exposure

Air quality is an integral component of environmental and public health. Construction and industrial processes are known to degrade the clarity and quality of respirable air, and the existence of air particulates is directly correlated with respiratory disease, heart disease, and cancer.

Exposure to excess particles in the air causes a number of health problems:

  • Increased respiratory symptoms, such as irritation of the airways, coughing, or difficulty breathing;
  • Decreased lung function;
  • Aggravated asthma;
  • Development of chronic bronchitis;
  • Irregular heartbeat;
  • Nonfatal heart attacks;
  • Premature death in people with heart or lung disease; and
  • Lung cancer.

PM 2.5 and Respirable Crystalline Silica

Mining, transporting, processing and using sand in the hydraulic fracturing process generate fine particles known as PM 2.5 (particulate matter with a diameter of 2.5 micrometers and smaller) as well as respirable crystalline silica ("respirable" means of a size that can enter the deep lung, this size range is called PM 4).

PM 2.5 concentrations are regulated by the EPA and DNR whereas no standards to protect the public from silica exposure have been established.

Of the different particles sizes to which the public is exposed (PM 10, PM 4, PM 2.5, PM 1), PM 2.5 is the size most closely associated with human health effects.

A 1995 American Cancer Society study, 2002 follow-up, and published 2012 study of six cities found that each 10-microgram per-cubic-meter increase in long-term average PM2.5 concentration was associated with,
a 4-14% increased risk of death from all natural causes,
a 6-26% increased risk of death from cardiopulmonary/cardiovascular disease, and
an 8-37% increased risk of death from lung cancer.
References: http://toxicology.usu.edu/endnote/1132.pdf, http://dx.doi.org/10.1289/ehp.1104660

 

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When respirable crystalline silica, in the form of particulate matter, is inhaled into the lungs it causes scarring of the alveoli and destroys macrophages. The body’s mucociliary escalator is incapable of removing crystalline silica from the lungs. This eventually leads to silicosis, a chronic lung disease, induced by the inhalation of crystalline silica. After a latent period of varying duration, lung cancer can result. Crystalline silica is classified as a human carcinogen.

An overview of questions about short- and long-term health effects of silica exposure is provided by the Canadian Centre for Occupational Health and Safety: click here.
Mechanism of silicosis (Smianalytical.com)
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Additional health effects from silica exposure include,

  • Tuberculosis
  • Autoimmune and Chronic Kidney Disease – Some studies show excess numbers of cases of scleroderma, connective tissue disorders, lupus, rheumatoid arthritis, chronic kidney diseases and end-stage kidney disease.
  • Non-Malignant Respiratory Diseases (other than silicosis) – Some studies show an increased incidence in chronic bronchitis and emphysema in workers.

 

Silicosis Deaths

Silicosis –a fibrosis (scarring) of the lungs. Silicosis is a progressive (long-term) fibrosis (scarring) of the lungs and leads to disability and death. About 200 people in the US are expected to die this year due to workplace exposure to silica (NIOSH 2008).

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Silicosis: Crude mortality rates by state, U.S. residents age 15 and over, 1991-1992.  SOURCE: National Center for Health Statistics multiple cause of death data. Population estimates from U.S. Bureau of the Census (http://www.cdc.gov/niosh/docs/96-134/pdfs/96-134e.pdf).

The National Institute for Occupational Safety and Health (NIOSH) reported 75 deaths in Wisconsin between 1996 and 2005 from silicosis, primarily among workers in manufacturing, construction and mining (Smathers, 2011). Based on the CDC map and NIOSH reported deaths, between 8-18 people are expected to die in Wisconsin from silicosis in 2011.

In a State of California Proposition 65 analysis of crystalline silica exposure during cat litter exposure, the following risk estimate was included: "concentrations associated with excess cancer risk of one in 100,000 would range from 0.54 to 15 µg/m3 silica dust" (http://www.oehha.org/prop65/CRNR_notices/safe_use/sud1.html)

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