Home algae growing is about as risky as sourdough, not motorcycles
Safety in Algae Home Experiments
A Bayesian hobbyist walks through the safety case for culturing Chlorella vulgaris at home: it sits outside the HSE pathogenic list, both CCAP and ATCC rate it Hazard Class 1 / BSL 1, and reported infections are rare and tied to wounds or factory-scale powder exposure. With basic hygiene and no drinking of samples, the author judges the risk closer to sourdough yeast than to riding a motorcycle, and plans to add Scenedesmus quadricauda and Dunaliella salina.
My subjective view is that growing chlorella is closer in risk to culturing yeast in sourdough, versus riding a motorcycle. If I am willing to ride a motorcycle, then I should be willing to grow some algae!