I have heard that the dust from MDF can be harmful, is this true?

The dust from MDF is no more harmful than ordinary wood sawdust. When working with any dusty situation it is a good idea to minimise your exposure to it by having good extraction and/or a dust mask as lungs don’t like dust.

If the MDF is sourced from New Zealand suppliers then formaldehyde emissions from a whole panel of raw board will be well below the World Health Organisation (WHO) guidelines for within a house.

Formaldehyde is a naturally occurring substance found in all kinds of living organisms including wood.  The body is quite capable of metabolizing it and it does not bioaccumulate.

Formaldehyde is also produced by wood fires, cars, lawn mowers, permanent press drapes, and some other fittings. It is only at really elevated levels found in manufacturing operations that it causes stinging of the eyes and nose. These are levels 10 times or more above the WHO guidelines for within a house.

If you are still worried, paint the cut surface as this significantly reduces the already minimal emissions.