For most people used to smoking a PAD? Unlikely to be a problem. You aren't absorbing 16 mg of nicotine out of every ml of liquid you vape, more likely only between 1/3 to 1/4 of it gets absorbed. How much someone absorbs seems to vary quite a lot on a person to person basis, which is why it's hard to tell anyone that "X" is exactly what you should be vaping if you used to smoke "Y" amount of cigarettes. You can take two people with the same smoking profile and one of them may get bowled over by 16 mg liquids, while the other person finds it's not enough and needs 24 mg instead to keep cravings at bay. It's something everyone needs to sort out when starting.
If it becomes problem you would notice things like rapid pulse, palpitations, nervousness or edginess. And if you just put it down the symptoms would disappear within a couple of hours.