A public agency may disapprove a project if necessary in order to avoid one or more significant effects on the environment that would occur if the project were approved as proposed. A lead agency has broader authority to disapprove a project than does a responsible agency. A responsible agency may refuse to approve a project in order to avoid direct or indirect environmental effects of that part of the project which the responsible agency would be called on to carry out or approve. For example, an air quality management district acting as a responsible agency would not have authority to disapprove a project for water pollution effects that were unrelated to the air quality aspects of the project regulated by the district.