Athletes with asthma don't require an exemption for salbutamol but there is a maximum limit set by WADA.
Salbutamol was brought to the spotlight last year when British cyclist Chris Froome was found to have elevated levels in his system during the Vuelta a Espana.
McCullum was eventually cleared of anti-doping violations in January 2017, but only after months fighting to avoid a ban.
It took a collection of medical evidence, testimony from medical staff and documented details of the polluted atmospheric conditions in Delhi that triggered his asthma attack, for McCullum to be granted a retroactive Therapeutic Use Exemption and avoid the ban.
McCullum said he had no ill feelings about the incident but wanted to set the record straight.
"I've heard this sort of rumbling around in the background for a while and I actually said to my wife, 'I don't know why we don't just deal with this now, I've got nothing to hide and it is better off just talking about stuff rather than having other people talking about it'. Otherwise it just grows and festers," McCullum told Stuff.
"As far as I am concerned it was just a matter of making sure we got everything signed off properly, rather than it being a failed drug test."
