Dust entry

Amorphous silica dust

Airborne non-crystalline silica particulate; diatomaceous earth is a naturally occurring amorphous-silica material that may contain crystalline silica depending on processing and composition.

Airborne form

dust

The form describes what is suspended in air at the point of exposure. A material can produce more than one form, such as dust during handling and fume during heating.

Health effects

eye irritationpneumoconiosispulmonary fibrosis concern when calcined or crystalline silica is present

Evidence

NIOSH identifies amorphous silica as the non-crystalline form of silicon dioxide and lists eye irritation and pneumoconiosis as symptoms, with the eyes and respiratory system as target organs.

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Exposure Limits; Exposure Routes; Symptoms; Target Organs · 1

NIOSH REL TWA 6 mg/m³. Exposure Routes inhalation, skin and/or eye contact. Symptoms irritation eyes, pneumoconiosis. Target Organs Eyes, respiratory system. Amorphous silica is the non-crystalline form of SiO₂.

The NIOSH/OSHA review states that some precipitated silica dusts are less toxic than quartz dust, while composition and processing matter.

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SILICA, AMORPHOUS · 2

There are numerous methods of producing precipitated silica; those that apply heat to siliceous products produce airborne dusts that are less toxic than quartz dust because the particles are generally sheathed in a molecular layer of amorphous silica.

NIOSH reports that calcination can convert diatomaceous-earth dust partially to crystalline form and produce pulmonary fibrosis.

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page 3 · Background · 2

When converted partially to crystalline form by calcination, the dust of diatomaceous earth produces pulmonary fibrosis.

Controls

exposure monitoring
local exhaust ventilation
enclosure
dust suppression
housekeeping
appropriate respiratory protection