Air pollution:

Malaysia has risen to the industrial age, not wanting to be left behind in the dark ages anymore, but at the cost of the environment. Many industrial zones have been approved by the government to be set up in mostly forestland and uninhabited areas. One very good example of the industrial zone is of Shah Alam in the state of Selangor. As a result, trees has been cut down to accommodate towards the building of large industrial factories.
Not only has the oxygen supply been decreased, these factories are spewing out poisonous gases in the course of its production.
Naturally, people would flock to industrial zones such as Shah Alam because of the high pay and high opportunity of jobs involved. Shah Alam is now one of the most densely populated areas as well as one of the most highly polluted areas in the country, and yet it is not the only one. One can imagine the amount of people who will be affected by the long side effects of the pollution from the gases.
The increasing amount of cars in Malaysia also has lent a hand in the pollution. Excess poisonous gases and heat are emitted daily (you should know the rest). Open air burning, despite it being banned by law, has not been heeded by the people of Malaysia. Burning is also the only way right now to get rid of the excess rubbish. Smoke and heat is released.