Last time I checked, people - including aircrew - breath around airports. Aircraft ECS systems use engine bleed air when they are on the ground and near airports. Aircraft exhaust on the ground includes significant amounts of engine lube oil (most turbine engines consume far more oil at/near idle then they do at power due to the way the lube systems work). If there is a problem with the air around airports, people - like pilots - who spend a lot of time at airports would be at risk.
If aerotoxicity is in fact an issue, how can you categorically state the issue isn't due to the air at the airport if no one is checking?