How does solar cell production pollute?

Depends on the kind of solar cell. Most types of solar cell use somekind of purified silicon substrate, and most types of solar cell use some combination of heavy metals, such as cadmium, tellurium, arsenic, indium, gallium, germanium, etc. In operation, solar cells cause no pollution whatsoever. But their production and what happens to them after use can cause pollution, and thus solar cells are certainly not without ecological footprint.

There are a great number of very toxic chemicals used to make solar panels. These chemicals, if disposed of incorrectly, can do incredible damage to the environment. Gases, such as Phosgene, are used in their manufacture. The firs visible symptoms of phosgene poisoning include death. Accidents with gases such as this are far easier to occur then say a nuclear accident and do happen.

Another major issue is the short life span of a solar panel. These panels lose output every year and after twenty years produce about 70% of what they did when new. They could quickly become a landfill disaster in the near future do the the volume of them needed to produce power for even one home.