A review in the journal Trends in Parasitology this week warns that cat poop could be an under-appreciated public health problem. E. Fuller Torrey of The Stanley Medical Research Institute and Robert Yolken of the Johns Hopkins University Medical Center warn that 1.2 million metric tons of cat feces is put into the U.S. environment each year, and that some of this poop is home to a parasite called Toxoplasma gondii.

“The accumulation of Toxoplasma gondii oocysts, found in cat feces, may be a much bigger problem than we realize because of their apparent long life and their association with some diseases,” said Torrey, the director of the Stanley Medical Research Institute.

Toxoplasma gondii has been linked in studies to schizophrenia, obsessive-compulsive disorder, rheumatoid arthritis, and brain cancer. Surveys have estimated that as many as three to 400 Toxoplasma gondii oocysts may exist per square foot in places where cats often poop.

The parasite is typically spread to cats from eating birds or rodents, and then spread into the soil from there. The owners of indoor cats have little to fear, but Torrey provides some recommendations for those whose cats enjoy outdoor privileges. He recommends being careful with litter boxes and wearing gloves when gardening. The authors of the review also speculate that young children may be at the greatest risk for infection, though the certainty of this is unknown. Also, Torrey states that the dangers of Toxoplasma gondii are not grave enough for every cat owner to run out and get tested, though “perhaps” pregnant women should.