local toxic response

A local toxic response occurs at the site where a chemical first contacts the body, unlike a systemic response which affects a different part of the body. For example, strong acids or bases can cause tissue corrosion on the skin or in the digestive tract upon contact. In contrast, methanol is absorbed and then converted into formic acid, which damages the optic nerve, leading to vision impairment—a systemic effect. Toxic responses can also be classified as reversible or irreversible. Some irritations, like those from formaldehyde gas, disappear once exposure stops, while others, such as silicosis caused by silica dust, result in permanent changes in the lungs.12