What are the differences in chemical leaching between indoor and outdoor plastics?

The chemical leaching processes of plastics differ significantly between indoor and outdoor environments due to varying exposure conditions. Outdoor plastics face continuous ultraviolet radiation from sunlight, which breaks down polymer chains and accelerates the release of additives like plasticizers, stabilizers, and colorants. Thermal cycling—daily and seasonal temperature variations—causes expansion and contraction that further promotes molecular degradation and leaching. Rainfall and humidity facilitate the washing out of water-soluble compounds and create hydrolysis reactions in certain polymers. Environmental pollutants such as acid rain or ozone can also catalyze degradation reactions.

Indoor plastics, by contrast, experience relatively stable conditions with minimal UV exposure (filtered through windows) and limited thermal fluctuation. While they still leach chemicals over time, the process occurs at a slower rate. Primary indoor leaching drivers include ambient temperature stability and exposure to indoor air pollutants rather than weather extremes. However, contact with cleaning chemicals or elevated surface temperatures can accelerate indoor leaching. Both environments show that additive-rich plastics (like PVC or vinyl) leach more readily than simpler polymers, but outdoor specimens typically demonstrate higher leaching rates and different chemical profiles due to accelerated weathering processes. The combination of UV, moisture, and thermal stress outdoors creates a more aggressive environment for polymer breakdown and subsequent contaminant release into surrounding environments.