The Department of Mines and Petroleum has investigated the two incidents and made several directives to Alcoa that it improve its asbestos management procedures.
At Alcoa's Kwinana refinery, seven workers were potentially exposed to asbestos during work to remove the roof on a tank on May 1.
Three workers at the Pinjarra refinery may have been exposed to white chrysotile asbestos in the press building on May 21.
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READ NOWAlcoa said the three were part of a group of seven and an angle grinder was used to remove small areas of coating from steel columns in preparation to install light brackets.
The coating is known to contain white asbestos, which does not present a risk of exposure unless it is disrupted through mechanical means.
Alcoa's director of health and chief medical officer Michael Donoghue said that for brief exposures, the health risk was extremely low.
Further, the risk to people more distant from the task and particularly to any family or friends, was negligible.
An occupational physician met with workers and health assessments were undertaken.
Alcoa has been directed by the Department to undertake a formal review of the format of its Asbestos Register to ensure information is readily available to all personnel.
The Australian Manufacturing Workers' Union (AMWU) renewed its call for an asbestos audit of Alcoa's WA operations.
AMWU state secretary Steve McCartney claimed up to 40 workers could have been exposed to the asbestos over a four-day period last month.
Mr McCartney said he had written to Alcoa to express his concerns and asked for an immediate and independent asbestos audit of Alcoa's WA operations.