What regulations apply to flying near blasting areas in Canada?
Blasting areas are not subject to particular regulation, they can be depicted on charts and/or announced by NOTAMs (code for blasting is WH, compliant to ICAO standard).
The blaster operator always ensures the area is clear of traffic prior to firing. The imminent blast may also be announced 4 and 1 minute(s) prior to the operation on 123.2 MHz. In case an aircraft is seen, the blaster operator will also use this frequency to inform the pilot of the blasting operation. See below for details.
It's pilot responsibility to remain clear of these areas:

  

Source: AIP Canada

Known permanent blasting activities can be depicted on VFR charts and announced by NOTAM until charts can be updated. From AIP Canada:

The “VFR Chart Updating Data” section of the CFS provides a means of
notifying VFR chart users of significant aeronautical information to
update the current VFR aeronautical charts. In this regard,
significant  aeronautical information is considered to be that which
affects the safety of VFR operation, e.g. obstructions, restricted
and advisory areas, blasting operations, cable crossings, and new or
revised control zones. New or  revised information of this nature,
which is required to be depicted on visual charts, is advertised by
NOTAM  until such time as the information can be published in the “VFR
Chart Updating Data” section of the CFS.  Subsequently, the NOTAM is
cancelled.

However temporary or itinerant blasting activities may not be advertised. From the Canadian AIM:

Another  concern  to  low  flying  is  the  blasting  operations
associated with the logging industry. The trajectory of debris  from
the blasting varies with the type of explosives, substance  being
excavated and the canopy of trees, if any. These blasting  activities
may or may not be advertised by NOTAM.

More details are given in the NOTAM Operating Procedures, chapter 5.5.5:

In the Pacific Region, NOTAM are not issued for blasting related to
logging activities under the following circumstances:

If using instantaneous blasting equipment.(The blasters will ensure the area is clear of all air traffic prior to the blast.)

If using a standard 6 minute-fuse and using aeronautical frequency radio. (The blasting operator will make two transmissions on 123.2 MHz
advising of the imminent blast. These transmissions will be at
approximately 4 minutes and 1 minute prior to the estimated blast.
These transmissions will include the geographical location referenced
to prominent landmark and the time to the blast.)


If blasters detect an aircraft in the immediate vicinity of a blast,
they will direct a radio transmission to that aircraft using aircraft
type and colour (&quot;Red and white helicopter, you are over an active
blast site; clear the area immediately.&quot;).
Blasters may elect to use both methods for added safety.
A NOTAM will be required if the blast site is within 5 nautical miles
of an aerodrome or if the blaster elects not to use either of the
above procedures. In any case, the NOTAM will have a maximum duration
period of 14 days.


Minimum safe altitudes don't take blast risk into account. From the Canada Air Pilot publication:

&quot;CYA, CYR and known blasting areas are not considered in the
establishment of MSA altitudes. For this reason, it is the pilot’s
responsibility to remain clear of these areas as applicable&quot;

Source: Canada Air Pilot
More: See this discussion: Quarry blasting not regulated for aviation safety purposes.