The inclusion of sex as a biologic variable is critical to understanding how individuals’ health and disease outcomes vary. When reading scientific papers, I often examine whether the study was completed in males or females, if the researchers specified sex, or if they analyzed for sex differences. Often, the sex of the model organism or cell line has not been disclosed, or if it has, only XY-derived samples were used. Prioritization of XY subjects in research leaves anyone not a cisgender male—“cisgender” refers to individuals whose gender identity aligns with the sex assigned to them at birth—at much greater uncertainty regarding health outcomes.
In 2016, the NIH mandated that sex be included as a biologic variable in scientific studies. While this action has proven beneficial and successful, we should continue to encourage individual fields of study like toxicology to rigorously assess for differences in susceptibility to chemicals and health outcomes by intersectional variables such as sex, race, gender, etc., to ensure proper protective measures for everyone. Our efforts to identify members of society vulnerable to environmental exposures should include assessing sex as a biologic variable beyond the binary of male and female, and analysis of gender should include considerations of trans, non-binary, and gender non-conforming individuals.