(Health problems) may be caused by pollution.Logical formLearned from4 sentences. (Pollution control commitments) can be costly.Logical formLearned from4 sentences. Some environmental factors may involve pollution.Logical formLearned from4 sentences. (Pollution levels) may improve.Logical formLearned from4 sentences. Environmentalists may be worried by a level of pollution.Logical formLearned from4 sentences. A parallel can be between pollution.Logical formLearned from4 sentences. Pollution may be caused by smoke.Logical formLearned from4 sentences. An (air pollution level) may pertain-to a world-city.Logical formLearned from4 sentences. Pollution may be caused by (automobile exhausts).Logical formLearned from4 sentences. (Air pollution) may cut visibility.Logical formLearned from4 sentences. An (air pollution) can be worldwide.Logical formLearned from4 sentences. (Water pollution) may contribute to a demise.Logical formLearned from4 sentences. A (water pollution) may hit pink dolphins.Logical formLearned from4 sentences. Pollution may be combined.Logical formLearned from4 sentences. A (pollution agency) may threaten legal action.Logical formLearned from4 sentences.