Said is smoking while working in the dirty water, at Sadarghat in Dhaka, Bangladesh. It is on the bank of Buriganga River. Rotten fruits and waste materials were floating in the water.  The air was also contaminated. But the boy was not at all thinking about the polluted environment. He was doing his job and smoking the cigarette in a very casual manner. Because of this polluted water and contaminated air not only the boy but also the people living surrounding the area might be affected by serious illness because of the bacteria, viruses, protozoa and parasitic worms. These worms cause many diseases that are spread by direct contact with faces or indirectly via contaminated food and soil. Diseases may also be transmitted through a carrier organism or vector. Vectors are organisms that do not cause diseases themselves, but carry or transmit disease-causing agents.