Factors that influence toxicity level may include but are not limited to:

• The particular organism exposed to the toxic chemical – different organisms react to toxic chemicals differently.
• The toxin’s ability to be absorbed by the organism – toxicity is higher in organisms that absorb the toxic chemical more easily.
• Life stage of the organism - infant, young adult or elderly adult
• Gender – physiological differences between men and women can impact toxicity levels of some chemicals.
• Form and intrinsic chemical activity of the toxin – the toxicity level of some substances is largely influenced by the form of the substance at the time of exposure
• Dosage – larger doses will almost always have a higher toxicity level.
• Dose-time relationship – exposure to large doses of a chemical does much more damage than exposure to a small dose just once or fewer times over a shorter window of time.
• Route of exposure – the exposure route impact the absorption and distribution within the body so chemicals that are highly toxic through one route of exposure may be harmless through another.
• Absorption levels – toxins that are more readily absorbed by the system will do more damage than toxins that are poorly absorbed.
• Presence of other chemicals – presence of some chemicals may increase the toxicity level of a substance while others may reduce its toxicity level.
• Metabolism of the organism – some organisms may detoxify toxic chemicals through their metabolic activity, while others may convert it to a more toxic or reactive form. 
• Health of the organism – chemicals typically display higher toxicity levels in organisms or individuals with pre-existing health conditions.
• Distribution within the body – lipid-soluble toxicants that can penetrate cell membranes more readily have a higher toxicity level.