The general philosophical methodology is the doctrine of the methods and techniques of cognition of nature, society and thinking, i.e. materialistic dialectics. Based on the idea of universal development, materialistic dialectics is oriented on its specific methods and techniques of cognition (analysis and synthesis, induction and deduction, historical and logical modeling, a systemic structural approach, etc.). Using these methods and techniques to know the essence of nature, society and the thinking, humanity discovered and formulated general philosophical laws and categories that are universal. Their universality is that they are applicable to any branch of scientific knowledge, to each scientific discipline.

2.1. LAWS AND PATTERNS - THEORETICAL BASIS OF HYGIENE

There are three basic laws of materialistic dialectics:

• the law of transition of quantitative changes into qualitative ones;

• the law of unity and struggle of the opposites;

• the law of negation of negation (the double negation).

The law of transition of quantitative changes into qualitative ones clearly «works», for example when a person inhales atmospheric air polluted with low concentrations of benzo(a)pyrene which are not harmful to health during short-term exposure. However, its long-term, near-threshold effect can lead to the development of lung cancer. Another example: since ancient times, there

has been the principle in medicine of «noli nocere» (do no harm). Any drug in the prescribed quantities (doses) has a positive therapeutic effect, but if this law is breached, treatment of the patient can lead to death.