(f)  Combating environmental pollution and providing proper sanitation systems; (g)  Combating drugs, psychotropic substances, smoking and substances that are damaging to health. Article 40 1.  The States parties undertake to ensure to persons with mental or physical disabilities a decent life that guarantees their dignity, and to enhance their self-reliance and facilitate their active participation in society. 2. The States parties shall provide social services free of charge for all persons with disabilities, shall provide the material support needed by those persons, their families or the families caring for them, and shall also do whatever is needed to avoid placing those persons in institutions. They shall in all cases take account of the best interests of the disabled person. 3.  The States parties shall take all necessary measures to curtail the incidence of disabilities by all possible means, including preventive health programmes, awareness raising and education. 4.  The States parties shall provide full educational services suited to persons with disabilities, taking into account the importance of integrating these persons in the educational system and the importance of vocational training and apprenticeship and the creation 23