Are micro- and nanoplastics from soil-biodegradable plastic mulches an environmental concern?

Micro- and nanoplastics are inevitably generated from biodegradable plastics during weathering and degradation. In this perspective article, we discuss whether micro- and nanoplastics generated from biodegradable plastics, especially soil-biodegradable plastic mulches, are of environmental concern. The environmental risk of micro- and nanoplastics generated from soil-biodegradable plastic mulches depends on size, concentration, time of exposure, and polymer characteristics (e.g., surface charge and hydrophobicity), similar to that of micro- and nanoplastics from conventional plastics. We argue that micro- and nanoplastics generated from soil-biodegradable plastic mulches will likely not cause environmental harm if soil-biodegradable plastic mulches are disposed of appropriately into soil or compost, because soil-biodegradable plastic mulches can degrade in a relatively short time, limiting the accumulation and exposure of generated micro- and nanoplastics in the terrestrial environment. However, micro- and nanoplastics from soil-biodegradable plastic mulches can be of concern when inappropriate disposal or off-site transport to atmospheric and aquatic environments happens. In such cases, the micro- and nanoplastics can no longer degrade readily and may have environmental impacts.