Impact on is a popular phrase used in writing, but it's important to vary your language to keep your text interesting and engaging. There are a number of synonyms for the word "impact on" that can help you communicate the same message in different ways. Alternative phrases could include "influence on", "effect on", "contribution to", "consequence for", "role in", "significance for", or "meaning for". Using a combination of these phrases can help you avoid redundancy and make your writing more precise, while providing a more nuanced understanding of the relationship between different factors. It's always helpful to have a broad vocabulary to communicate your ideas effectively.