Hi s.guo1,
I wanted to add a few notes for you as well, although Iām not Manimal. 
Regarding dust mites, Iāll add that the key is to keep your skin cell population as low as possible to keep their food source low, so washing sheets and keeping floors swept really helps. Also, a sleeping environment that is cool and low in relative humidity is also important.
Regarding EMFs, you can see some comments about innersprings and electromagnetic (EMF) fields in posts #2 and #3 here. Itās certainly not something that would concern me in any way, but I donāt dismiss Manimalās opinion on the topic.
Iām certainly not a health professional or an expert in electromagnetic fields but EMF fields from mattress innersprings are a very controversial subject and there are certainly some people that believe they are harmful although Iām not one of them. I have seen and read many articles that include many of these types of comments about innersprings being a āhealthā issue because of electromagnetic fields ā¦ but I have never seen any specific evidence that is compelling to me and most of these types of articles use some very non specific anecdotal stories or what I would consider to be some questionable correlations that donāt provide any clear evidence that would directly relate to innersprings or metal frames. I would personally be more cautious with āactiveā electromagnetic fields (such as living close to high tension wires, holding a cell phone too close to your head, or sleeping near active electrical fields or wiring as examples) ā¦ but I personally wouldnāt have any issues with sleeping on an innerspring in terms of health or safety (although I recognize that there are certainly others that have a different opinion).
A forum search on electromagnetic (you can just click the link) will bring up more comments and feedback about EMFās as well to add to your research.
Phoenix