Sick Building Syndrome is probably much more common than is generally appreciated. I hope they figure this out, whatever the actual answer or answers turn out to be.
NZ some younger polichickens suggested rental WOF (warrant of fitness) which IMO is great idea. We already do that for cars every year and it costs almost nothing. For housing it would cost something like 0.5% of your rent.
The insurance industry will prevent that any scientific study will be taken seriously.
Most articles in mainstream media about Multiple Chemical Sensitivities or Sick Building Syndrome will continue to downplay the risks.