How old is Mr. Loomis in Z for Zachariah?

There is no clear answer to this question, as Mr. Loomis' age is not specifically mentioned in the book Z for Zachariah. However, it is mentioned that before the global disaster that wiped out most of the population, Mr. Loomis was a scientist who worked for the government. It can be assumed that he was at least in his late thirties to early forties at the time of the disaster, as he had already established his career and had enough expertise to be a valuable member of a government research team. Over the course of the novel, he demonstrates knowledge and experience that suggest he is middle-aged or older. However, without a specific age given by the author, it is up to interpretation.