It is highly inflammable and produces environmentally harmful sulfides. And the greatest problem remains supply--unpredictable price changes and uncertain political factors make petroleum an unreliable energy source.
目前用石油當能源，主要的顧慮卻不在安全或汙染方面；最大的風險還是它的價錢因國際政治、經濟因素瞬息萬變，叫人捉摸不定；供應來源也有較早費竭的威脅。