Is there nicotine in cannabis

No, it does not. But if it is rolled up with tobacco, the smoke will contain nicotine. There's more.

Though marijuana doesn't containe nicotine, it does have a number of hazardous chemicals in it. The problem is that when combustion occurs in smoking materials, the combustion process does not completely reduce the burned material to ash. The partial comubustion of the materials results in dozens (hundreds, actually) of different chemical compounds, as well as carbon monoxide, and soot and other particulate matter are present in large quantities.

Breathing any kind of smoke is not a good idea, particularly in heavy concentrations. A wiff of the grill and the campfire are not to be missed, but we don't stand in a cloud of smoke and try to breathe. Our lungs don't like that. And with smoking - the deliberate inhalation of combustion byproducts - we tend to "hold in" the smoke longer. Particularly when smoking marijuana. This allows greater THC uptake (which is the reason it is smoked) but also allows greater uptake of all the other junk in the smoke. And more particulate matter, those tiny particles of soot and such, have more time to get stuck to something and then are not exhaled.

There are a number of organic compounds that are known carcinogens in marijuana smoke. Sure, there's no nicotine, but some of the other cancer causing chemicals in tobacco are present in cannibis smoke - and at twice the levels they are in smoke from tobacco. Smoking anything is a bad idea if you wish to avoid "dirty" lungs. Breathing smoke is unhealthy, regardless of what is burning. Smoking is a fast way to maximize uptake of THC, but it comes at a price.

Make whatever choices you wish. The Word on the street is that THC is a muscle relaxant, appetite enhancer and a couple of other thing. But don't kid yourself. Smoke - the partially combusted products of burning something - isn't good for you. Firefighters have known this for decades.

No doubt both have harmful attributes. However when considering Ciggs over Cannabis, I know of no one but maybe Rastafarians that smoke pot all day. I smoke ciggs and smoke terribly at 40-50 ciggs a day, approx 50 grams. When I smoked pot, a big day would be three joints and most occasions were a joint. So when considering the bad things of both, one is used much much more than the other.