A traffic jam is a very unpleasant experience. Not only could the gridlock cause you to arrive late to an important event such as a meeting, a job interview or an exam, but it can also cause air pollution levels to increase due to the fact that the idling cars are producing more toxic emissions.

Traffic jams are very disappointing, not only because you could arrive late at an important event such as a meeting, a job interview, or an exam; but also because air pollution increases due to the fact cars are giving off a lot of gas and smoke.

Bruces is the best answer with a slight correction in the front, When you start a sentece, you use a capitol letter, some commas if need be and a period at the end.

Car jams are very frustrating! Not only can they cause you to arrive late at an important event, such as a business meeting, job interview or exam, they also contribute to our increased air pollution problems. The reason for this is there are so many cars traffic jams giving off harmful emissions and smoke.