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- substances, which penetrate into the human body through the gastrointestinal
tract;
- substances, which penetrate into the human body through the skin and
mucous membranes.

c) According to State Standard ГОСТ 12.1.007-76 “Harmful substances,
their classification and general safety requirements” there are four classes of risk by
the degree of impact of harmful substances on the human body (Table 7.2):
Class I - extremely dangerous substances;
Class II – especially dangerous substances;
Class III – moderately hazardous substances;
Class IV – low-hazard substances.
The class of danger of the harmful substances is determined according to the
set rules and parameters listed in Table 7.2.
The distribution of harmful substances to hazard class is conducted by the
parameter, which has the highest hazard class

Table 7.2 – Classes of harmful substances
Name of indicators Standard for hazard class
I class IІ class ІІІ class IV class
Maximum allowable concentration Less than 0.1-1.0 1.1-10.0 More than
(MAC) harmful substances in the air 0.1 10.0
of the working zone, mg/m 3
The average lethal dose when Less than 15-150 151-5000 More than
injected into the stomach, mg / kg 15 5000

The average lethal dose when Less than 100-500 501-2500 More than
applied to the skin, mg / kg 100 2500

The average lethal concentration in Less than 500-5000 5001-50000 More than
air, mg/m 3 500 50000
Ratio possible inhalation poisoning More than 300-30 29-3 Less than 3
300
Area of acute poisoning Less than 6.0-18.0 18.1-54.0 More than
6.0 54.0
Area of chronic poisoning More than 10.0-5.0 4.9-2.5 Less than
10.0 2.5

Main Measures against Harmful Substances:
1) Technical measures include replacement of toxic substances with non-
or less toxic; automation, mechanization, application of remote control in order to
eliminate the contact of the employee with toxic substances; sealing of the equipment
using local and general ventilation;
2) Sanitation measures include systematic control of toxic substances in
the air; use of individual protection means; keeping scheduled work-rest regimen;
3) Medical preventive measures include preliminary and periodical
medical examinations, treatment at health resorts.

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