## 3 Results
The result is justified by the machines park of each company, which belongs to the latest generation [42]. The chemical risk assumes an important role, as expected, since the operators come into contact with substances which significantly affect their health. The purchase of new equipment and the use of additives and chemicals not harmful to human health rewarded company 4. It is therefore confirmed the need for adopting protective and preventive measures to reduce chemical risks, especially for plant 3, which has the worst workers' health performances. According to Figure 4, the noise in cement plants represents the second factor of risk after the chemical one: mechanical equipment produces high noise, especially if they are not compliant with noise regulations [44]. It is therefore important to quieter equipment and machinery, and use hearing protection to reduce this risk [45; 46]. Figure 5 represents the results obtained about the socio-economic issues. Figure 4: Level II: workers’ health results. As regard as the energy consumption, the analysis considered water and electricity consumption. Most of the observed differences are related to water consumption, since electricity consumption for cements which have the same \(R_{ck}\) is not appreciable [47]. The realization of closed rings circuits permits to substantially reduce water consumption, during the cooling phase [48]. Plant 2 has the best results, also related to the reuse of rainwater in the production cycle, while companies 3 and 4 have the worst performances because they did not implement measures to recycle and reduce water consumption. As regard as the unit price, cement 4 is the most convenient, the opposite of cement 3 which is the most expensive. The results shown in Figures from 3 to 5 have been summed for each criterion listed in level I. This procedure allowed the selection of best cement, as represented in Table 25.  
Figure 6 graphically represents the final results listed in Table 25. For each cement powder the contribution of each criterion of level I is represented. Cement 4 is the most sustainable, and its performance is affected by the workers' health criterion. Indeed, this contribution is 0.409, more than 33.4% of the overall result, and considerably more than \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Best Cement** & **Environment** & **Workers’ Health** & **Society** & **Final Results** \\ \hline
**Cement 1** & 0.149 & 0.133 & 0.059 & **0.341** \\
**Cement 2** & 0.090 & 0.110 & 0.057 & **0.257** \\
**Cement 3** & 0.887 & 0.045 & 0.026 & **0.958** \\
**Cement 4** & 0.755 & 0.409 & 0.055 & **1.220** \\ \hline \hline \end{tabular}
\end{table} 
Table 25: Contribution of elements of level II to the main goal. Figure 6: Level I: comparison between cement powders. the workers' health contribution for the other cements (Figure 4). The results highlight the importance of considering more criteria in the analysis:  
* Considering only environment (blue lines), cement 3 would be the best;
* Considering only socio-economic (green lines) results, cement 2 would be the best. The AHP analysis ensured a good compromise between the three criteria (environment, workers' health and society) applied on the cement production of four Italian companies, which are already placed at a high level in terms of technological and procedural innovation [49]. As it can be observed from all previous analyses, the results obtained from the AHP analysis could be useful to support the process of deciding the \"best option\", because it allows a comprehensive, critical and unbiased analysis, which could be efficiently replicated at different level [50] in public bids.