Izmerov returned to Moscow in 1971 and was elected head of the research Institute of occupational health and diseases (in Academy of Medical Sciences, the leading Institute in this field in the USSR and in RF, and the world's oldest scientific institute of occupational diseases).
As the head of the Institute (director in 1971–2012, scientific director in 2012-2015) he has done a lot to improve the work of the Institute: the development of fundamental research in the field of occupational health, the development of permissible exposure limits, the development of manuals and textbooks, the implementation of research results in the practice of protection of workers.
Some of the toxicological research results were used by the World Health Organization (WHO) and the International Programme on Chemical Safety.

The work of the Institute (and other similar institutions) received a positive assessment from the American specialists earlier.

The director of the Institute focused the attention of his experienced and qualified staff on the development of methods of prevention of occupational diseases; principles and methods of improving working conditions, the environment, and saving the health of workers.
The Institute became one of the leading occupational health institutes in the world.
Izmerov signatories of the WHO "Declaration on Occupational Health for All" in 1994 as a director of a leading national OHS Institute.

The Institute established the laboratory of women's occupational health (in 1974), the Department of social and hygienic research, equipped with modern technology and successfully implementing the latest technology.

The specific features of the Soviet centralized planned state management led to the fact that the scientific developments of the institute became the requirements of legislation very often, and them were implemented in the enterprises.
A characteristic feature of these works in the field of occupational health was their focus on the elimination of the causes of diseases and their prevention.
This occupational medicine was integrated with the public health system and with the general sanitary hygiene services.
According to Western hygienists, this feature led to the fact that the developed requirements were "too idealistic."

Izmerov became a doctor of medical sciences in 1973; professor in 1977; and a corresponding member of the Academy of Medical Sciences in 1980.
He continued international activities as the Institute director.
Izmerov became an academician in 1986.

The Institute developed exposure limits for chemicals, physical hazards.,
and non-toxic dust (which causes pneumoconiosis).
If the low level of science and technology did not allow to fulfill the requirements, then the Institute has developed a classification of working conditions according to the degree of danger (classes of work); and led the development of alternative methods of protecting health (aka.
protection by reducing exposure time; protection by distance and shielding, etc.).
Izmerov led the development of risk assessment methods for the cases of the employee's simultaneous exposure to the various types of occupational hazards.
The Institute was established museum of occupational hygiene in 1987
Nikolai Izmerov published over 500 journal papers (and other publications), several textbooks and manuals; and created a school of hygienists.
27 candidates and 32 doctors of science were trained under his leadership and during his consultations.
He was editor of the articles in the Great Medical Encyclopedia, and ILO OHS Encyclopedia; and chief editor of the magazine "Occupational Health and Industrial Ecology".
Izmerov worked at the First Moscow State Medical University as head of the department of occupational health.
Izmerov returned to Moscow in 1971 and was elected head of the research Institute of occupational health and diseases (in Academy of Medical Sciences, the leading Institute in this field in the USSR and in RF, and the world's oldest scientific institute of occupational diseases). As the head of the Institute (director in 1971–2012, scientific director in 2012-2015) he has done a lot to improve the work of the Institute: the development of fundamental research in the field of occupational health, the development of permissible exposure limits, the development of manuals and textbooks, the implementation of research results in the practice of protection of workers. Some of the toxicological research results were used by the World Health Organization (WHO) and the International Programme on Chemical Safety.
The work of the Institute (and other similar institutions) received a positive assessment from the American specialists earlier.
The director of the Institute focused the attention of his experienced and qualified staff on the development of methods of prevention of occupational diseases; principles and methods of improving working conditions, the environment, and saving the health of workers. The Institute became one of the leading occupational health institutes in the world. Izmerov signatories of the WHO "Declaration on Occupational Health for All" in 1994 as a director of a leading national OHS Institute.
The Institute established the laboratory of women's occupational health (in 1974), the Department of social and hygienic research, equipped with modern technology and successfully implementing the latest technology.
The specific features of the Soviet centralized planned state management led to the fact that the scientific developments of the institute became the requirements of legislation very often, and them were implemented in the enterprises. A characteristic feature of these works in the field of occupational health was their focus on the elimination of the causes of diseases and their prevention. This occupational medicine was integrated with the public health system and with the general sanitary hygiene services. According to Western hygienists, this feature led to the fact that the developed requirements were "too idealistic."
Izmerov became a doctor of medical sciences in 1973; professor in 1977; and a corresponding member of the Academy of Medical Sciences in 1980. He continued international activities as the Institute director. Izmerov became an academician in 1986.
The Institute developed exposure limits for chemicals, physical hazards., and non-toxic dust (which causes pneumoconiosis). If the low level of science and technology did not allow to fulfill the requirements, then the Institute has developed a classification of working conditions according to the degree of danger (classes of work); and led the development of alternative methods of protecting health (aka. protection by reducing exposure time; protection by distance and shielding, etc.). Izmerov led the development of risk assessment methods for the cases of the employee's simultaneous exposure to the various types of occupational hazards. The Institute was established museum of occupational hygiene in 1987
Nikolai Izmerov published over 500 journal papers (and other publications), several textbooks and manuals; and created a school of hygienists. 27 candidates and 32 doctors of science were trained under his leadership and during his consultations. He was editor of the articles in the Great Medical Encyclopedia, and ILO OHS Encyclopedia; and chief editor of the magazine "Occupational Health and Industrial Ecology". Izmerov worked at the First Moscow State Medical University as head of the department of occupational health.
Nikolai Izmerov