There are still flaws in our scientific understanding and technology, however, so we still have environmental problems. Another factor is budget: if something needs to be done urgently or if it is expensive, it may not be done. The public interest can also be an obstacle – some people may resist measures that they see as schemes to make them pay. In addition, political factors can play a role – for example, if someone in power opposes action on the environment, he or she will probably try to block measures proposed by authorities on environmental matters.