Ranking chemicals according to their potential environmental hazard is a well accepted preparatory step in risk assessment. A study of Halfon et al. ranked pesticides by applying simple tools on the partially ordered set (poset) induced by chemical properties as proxies for their groundwater contamination hazard. In this contribution, we present some developments in the field of partial order theory which prove to be helpful in applications where a ranking is needed. Whereas in the former study a classification of the pesticides in only four classes was obtained, in the current contribution tools are used that aim at a greater differentiation to support decision makers and to allow for comparison with monitoring results. In order to quantify how close the result of each tool is to a ranking of the pesticides, a linearity index is introduced.