Question:
In my search for suitable paints, I often come across paints that contain isothiazolinones as
a preservative. Are they harmful to human health?
IBN Answer:
Isothiazolinones (also known as isothiazolones) are biocidal active ingredients and are commonly used as in-can preservatives (to protect paints and coatings during storage) and film preservatives (coating protectants) in paints and other water-based products, such as varnishes, stains, ready-mix plasters, adhesives, sealants, cleaning products, and personal care products. Because they can cause allergic reactions and skin eczema, their use can be problematic, especially because they continue to be released into the indoor air after the drying process is complete. For paints, in-can preservatives can often be avoided if dry powders are mixed with water on site instead of using ready-mixed paints, as was common practice until a few decades ago (source: Building Biology Online Course).