Background:

It's known that heavy metals are among the most toxic micropollutants. In aerosol particles, heavy metals can be present as chemical compounds and bound to organic matter (ligands). Unlike chemical compounds, the bond between microelements and organic matter is weaker and can be easily destroyed by bacteria releasing biologically active forms of micropollutants.

Objective:

To evaluate the impact of the level of association between aerosol heavy metals and organic matter on the incidence of upper respiratory infections in children attending kindergartens.

Methods:

Microelemental analysis of aerosols was done using dust samples collected from 22 kindergartens. Concentrations of 11 trace elements were measured by an X-ray fluorescence (ED-XRF) spectrometer. The organic matter content of the dust samples was determined by the extraction method. The organic fraction of each trace element was calculated based on differences in mass and microelemental concentration of the samples before and after extraction (solid fraction). The annual incidence of respiratory infections in each kindergarten was calculated based on medical records data.

Results:

A significant correlation was found between indoor concentrations of vanadium (V) and nickel (Ni) and the annual incidence of acute upper respiratory infections in children attending kindergartens. At the same time, the highest detected concentrations of these trace elements were 27.58 ppm (V) and 67.60 ppm (Ni), and did not exceed the permissible age-non-specific concentrations. The association of these microelements with organic matter in dust samples was among the highest for the 11 studied microelements, reaching 94% (V) and 78% (Ni), indicating a potentially large release of biologically active forms of heavy metals.

Conclusions:

The concentrations of V and Ni in dust samples collected in kindergartens are related to the annual incidence of upper respiratory infections in preschool children. The association of heavy metals with organic matter in aerosols, which is easily broken down by bacteria in the respiratory tract, is apparently a significant primary source of the biological activity of these microelements in the human body. It can explain the harmful effects of relatively low concentrations of aerosol heavy metals on child health.