Pollution can be in air.Logical formLearned from21 sentences. Some forms can be constituted-of-or-filled-with (air pollution).Logical formLearned from21 sentences. A threat can be constituted-of-or-filled-with pollution.Logical formLearned from21 sentences. Pollution can be chemical.Logical formLearned from21 sentences. Pollution can be localized.Logical formLearned from21 sentences. Pollution may undergo a treatment.Logical formLearned from21 sentences. An (air pollution problem) can be serious.Logical formLearned from21 sentences. Concerns can be about pollution.Logical formLearned from21 sentences. Pollution may reach levels.Logical formLearned from21 sentences. Natural resources may undergo pollution.Logical formLearned from21 sentences. (Air pollution) can be severe.Logical formLearned from21 sentences. A person may see pollution.Logical formLearned from21 sentences. Concern can be about (air pollution).Logical formLearned from21 sentences. A solution to pollution can be a dilution.Logical formLearned from21 sentences. Pollution can be from coal-fired (power plants).Logical formLearned from21 sentences.