Amongst persistent organic pollutants, the polychlorinated biphenyls are the most common. They were mass-produced and used since 1929. Till the end of industrial production in 1986, about 2 million tons of polychlorinated biphenyls were produced in the world.
Polychlorinated biphenyls have a number of unique physical and chemical properties: exceptional thermophysical and electrical insulating characteristics, heat resistance, inertness with respect to acids and alkalis, fire resistance, good solubility in fats, oils and organic solvents, high compatibility with resins, excellent adhesive ability. This resulted in their widespread use as dielectrics in the transformers and capacitors, hydraulic liquids, coolants and refrigerants, lubricants, paint components, varnishes and adhesives, plasticizers and fillers in plastics and elastomers, flame retardants, solvents.
At the same time, they are one of the few truly global pollutants. They were detected in small but measurable concentrations in almost all marine, plant and animal organisms. They can enter the body through the lungs, gastrointestinal tract, and skin. Once penetrated into the body with the food or air, polychlorinated biphenyls are circulating with the blood and accumulating in the fatty tissues and some organs such as the liver, kidneys, lungs, adrenal glands, brain, heart and skin.
The issues are considered concerning optimal accounting of emissions of polychlorobiphenyl into the environment taking into account its half-life. Two optimization problems are formulated and solved related to the rational accounting of polychlorinated biphenyl harmful effects on the environment.
In accordance with the solution of the first problem, the risk of the effect of the polychlorobiphenyl emissions to the atmosphere on the human body in the specific populated area will be minimal if there is a direct proportional relationship between the attenuation coefficient and the population of the zone under consideration.
As per the solution of the second problem, which consists in estimating the integral value of the additional Weibull function `W'(t)`, it was identified that the target value will be minimal if there is a direct proportional relationship between the half-life of the considered set of polychlorobiphenyl congeners and the time of beginning of their use.