A numerical 0D global model is developed with an aim to study the influence of air and water vapor impurities on electron energy distribution function and chemical composition of atmospheric pressure helium plasma, focusing on the main reactive oxygen and nitrogen species. Model includes 1488 reactions among 74 species, taken from the literature. Rate coefficients for electron impact processes are calculated using two-term Boltzmann solver BOLSIG+, with cross section data mainly taken from Quantemol-DB database. The main channels for production and consumption of reactive species are examined for a constant electron concentration 1010 cm-3 and electron temperature 2 eV. We have performed parametric study where mole fraction of air and water vapor were varied in the wide range, using data from the literature. The calculations are done for 100 ppm and 10000 ppm of air in plasma, and for each of these values the content of water vapor was 100 ppm, 1000 ppm, 2000 ppm etc. to 8000 ppm. Through the influence of these contents on electron energy distribution function (EEDF) and appropriate rate coefficients, the variations of the most important production and consumption processes for O, OH, N and NO are analysed in detail. Results show that increasing of air and water vapor contents require higher E/N values to achieve given mean electron energy, rising the energy tail of EEDF and the values of rate coefficients for the electron impact processes with high energy thresholds, such as dissociation of O2, N2 and H2O, important for initial production of O, OH, N and NO. Thus, for the same amount of water vapor, increasing of air content in plasma leads to higher concentration of OH radical and consequently higher level of H2O2. For the same amount of air, higher content of water vapor generally leads to decrease of O and N concentrations through chemical reaction with OH radicals.