How does it actually harm our body?
A+T+R1 is the only governing constraint on light's interaction with a material. Consider a red glass material. The red means that it absorbs certain colors. Glass is still reflective. And you can see through red glass.
Use a pressurized water extinguisher. (The original super soaker!) Make sure you fill it with FRESH WATER. Charge it with some pressure with an air compressor, but don't feel like you have to give it a full charge. Let 'er rip! I work for a fire extinguisher company and we have had some fierce battles with pressurized water units. (Just don't aim at his face!)