Table 1. Study descriptors used as covariates.

Type indicates categorical or continuous study descriptors used as covariates in multilinear regression (MLR). The conditions defined per study descriptor are described, along with any mathematical adjustments made.

Study descriptor	Type	Conditions	Adjustments
Chemical	Categorical (factor)	identified as a “dsstox_substance_id”
Study Type		identified as subacute (“SAC”), subchronic (“SUB”), or chronic (“CHR”)
Species		identified as “rat”, “mouse”, or “dog”
Administration Method		identified as “feed”, “gavage/intubation”, “water”, “capsule”, “not specified" [oral], "diet", "whole-body"	included in MLR for full endpoint target dataset; not included for the previously curated ACM dataset due to lack of sufficient levels
Dose Number	Continuous	number of non-control, treatment-related doses
Dose Spacing		the average distance between each dose in the series, centered around the mean
Study Year		Year the study was reported, centered around the mean	NA changed to mean
Substance Purity		% substance purity reported, centered around the mean	NA changed to mean