A quick look suggests that this stuff can be flammable, may release toxic gases/vapors/fumes if burned, "very toxic to aquatic life" and "very toxic to aquatic

A quick look suggests that this stuff can be flammable, may release toxic gases/vapors/fumes if burned, "very toxic to aquatic life" and "very toxic to aquatic life with long lasting effects", and may cause harm to breast-fed children. Other examples of hostile architecture like spikes, razor wire, cameras or sprinklers are still annoying, but may be less likely to have environmental impacts or create hazards to nearby innocents.