Pollution can be described as contamination of air, water and soil by introduction of a contaminant into a natural environment, usually by humans that are harmful to living organisms. The most common forms of pollution are air pollution, water pollution, agricultural pollution and land pollution. Methane expended from livestock, carbon emissions from transport, and oil and waste dumped into the ocean are all forms of pollution. Pollution is one of the largest causes of illness and death, affecting more than one billion worldwide. Women and children are especially at risk, and pollution’s adverse effects are felt more deeply in the developing world.