Quite a lot of recent traffic has been on the subject of various organic
acids (especially formic and oxalic) for the treatment of varroa.  Some
months ago I prepared some notes about the health and safety aspects of
these chemicals for my local association.  Some of the information that I
collected is presented below for the information of beekeepers
contemplating the use of these acids.

In brief-be very careful in handling these acids; these are dangerous
substances that can easily damage your health:

Formic Acid.

Formic acid is corrosive to all body tissues.  Contact with skin or eyes
will give rise to damage immediately and must be prevented. When handling
the acid, impervious protective clothing is required, including gloves, and
chemical safety goggles are required.  The vapour causes severe irritation
of the respiratory tract if inhaled.  The threshold concentration of the
acid vapour for short term exposure is 10 parts per million.  This is a low
value  and so a suitable full face respirator should be used, unless the
acid is used in a very well ventilated area.

Lactic Acid

Lactic acid is a crystalline substance readily soluble in water.  Although
this is generally regarded as a less hazardous substance it can cause
allergic reactions and irritation to skin, eyes or digestive tract.  It
also has a relatively low flash point and should be treated as an
inflammable substance. When handling the acid it would be sensible to use
chemical resisting gloves, and chemical safety goggles, and to work in a
well ventilated area.

Oxalic Acid

Oxalic acid is corrosive to tissue, and can also cause kidney damage if
swallowed.  A fatal dose is estimated by some authorities to be as low as 5
to 15 grams (about one third of an ounce).  It can cause severe irritation
of the respiratory tract if the fumes are breathed in.  The threshold value
for concentration in the air for short term exposure is 2 parts per
million.  Unless the area in which the acid is being used is extremely well
ventilated to keep the concentration below this low value a half face
respirator with an organic vapour cartridge is required to prevent
damage.  Even then care is required to keep the acid vapour concentration
below 20 parts per million.  When handling the acid, impervious protective
clothing is required, including gloves, and chemical safety goggles are
required.

Regards



Mike Rowbottom

Harrogate
North Yorkshire
UK




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