This paper analyzes the improvement of ambient air quality indicators by monitoring the NOx concentration in one of the most polluted areas of Bucharest, using the statistical method "SIX SIGMA" (6σ). By applying the methodology of this statistical approach, the aim is to reduce non-conformities within the specified limits (according to the standards and legislative norms in force) and respectively, to ensure maximum efficiency (99,99%), equivalent to a yield of 3.4 defects per million opportunities (DPMO). As high concentrations of air pollutants have a major impact on human health, the most harmful effect has been found to be caused by nitrogen dioxide (NO2), mainly from ground-level ozone. Using the "6σ" method, the optimal solutions for eliminating non-conformities and implicitly for reducing the NO2 concentration and ensuring the improvement of the ambient air quality can be identified.

The present paper considers the use of the results of the evaluations carried out by applying the Six Sigma statistical method to improve the vulcanization times of elastomeric composites on the external manufacturing cycle of several size types of car tires. This statistical approach aims to verify the distribution of the measured values of the external vulcanization times between the normal specification limits to optimize them and improve the performance, efficiency, and quality of the automotive tire vulcanization processes. Through the analysis carried out, the operations that caused delays and defects were identified, a program of corrective measures was carried out and after its execution, the fulfillment of the purpose was verified, namely the optimization of external vulcanization times and reducing the number of faulty tires. The new measured values of the vulcanization times were within the normal limits of the imposed specifications (LSS = 2.5). This situation corresponds to achieving a maximum level of performance and represents the successful completion of the quality improvement project.

The paper presents an environmental impact study in a real case: a landfill containing hazardous substances, held by an economic operator in an area near a city. The sludge storage was monitored taking into account three main impact factors: soil, groundwater and leachate. The actual environmental status of the storage area is assessed by calculating these impact factors before and during ten years of storage and the global pollution index.