Haze is phenomenon where dust, smoke and other dry particles obscure the clarity of the sky. Indonesia's annual burn-off to clear land for agriculture causes a haze and the smoke has blown over to Singapore. The Pollutant Standards Index, or PSI, provides a uniform system of measuring pollution levels for the major air pollutants. PSI values are derived from measured pollutant concentrations, which are reported daily in all urban areas of the United States with populations exceeding 200,000. Short term exposure can cause headaches, dizziness, drowsiness and tiredness, while long term exposure can cause eye and respiratory tract irritation. Singapore's repeated offers to assist with fighting fires, but Indonesia decline it. They could start to nationalize their agricultural sector and provide environmental friendly ways to fertilize their crops. They could penalize those whom grow crops on burnt down forest.