The Silica/Asphalt Milling Machine Partnership – All Good Things Need Not Come to an End

Posted on by Duane Hammond, MS, PE


A recent ceremony at World of Asphalt 2015 celebrated the success of the Silica/Asphalt Milling Machine Partnership’s accomplishments to develop and validate engineering controls for silica dust in asphalt milling operations. The partnership between government, industry, labor was coordinated by the National Asphalt Pavement Association over the past decade to design, test, and implement engineering controls for asphalt milling machines to effectively reduce potential silica exposure below NIOSH’s recommended exposure limit (REL) of 0.05 mg/m3.

Approximately 367,000 U.S. workers are employed in highway, street, and bridge construction and are at risk of exposure to respirable crystalline silica.[i] Workers use a variety of machinery when removing and recycling asphalt pavement including a cold-milling machine which has toothed, rotating cutters that grind and remove pavement for recycling. Workers can breathe in the dust generated from the cold-milling machines which often contains respirable crystalline silica. Breathing respirable crystalline silica can cause silicosis, a debilitating and potentially fatal lung disease.

One product of the Partnership is the NIOSH document, Best Practice Engineering Control Guidelines to Control Worker Exposure to Respirable Crystalline Silica during Asphalt Pavement Milling, which provides recommendations that include ventilation controls in addition to water sprays used to cool the cutting teeth of milling machines, lessening silica dust exposure. The document also provides machine manufacturers guidance for evaluating current and future dust controls.

The Partnership has been lauded as the gold standard for industry, labor, and government cooperation like the Asphalt Paving Partnership before it. If those involved in the Partnership would like to provide comments below on what made this such a unique endeavor, we would love to hear them. We would also be interested in hearing from you if you think your industry could benefit from a similar collaboration.


Duane Hammond, MS, PE, is a Mechanical Engineer in the NIOSH Division of Applied Research and Technology.

[i] U.S. Census Bureau [2007]. Industry statistics sampler. NAICS 237310. Highway, street, and bridge construction. Washington, DC: U.S. Department of Commerce.


Posted on by Duane Hammond, MS, PE

4 comments on “The Silica/Asphalt Milling Machine Partnership – All Good Things Need Not Come to an End”

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    The silica/asphalt mill, is something really interesting, specially in all this remote areas. In Mallorca, we have done a test with a similar system with excelent results

    A very interesting and advanced article on asphalt and silica mill with advances in technology. Thanks for sharing such informative article.

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Page last reviewed: April 15, 2021
Page last updated: April 15, 2021