Question

what problems can we have from smoke coming out of vehicles

Answer 1

 Smoke emissions mean the engine has deteriorated and damaged. So, it leads to wastage of fuel too. Upon inhalation, this smoke that  consists of carbon dioxide gas combines with haemoglobin in blood to form carboxyhaemoglobin which is prime cause of cancer.  This smoke also depletes the ozone layer and causes air pollution. Smog contains smoke only primarily.