grammer

First, "grammar" is commonly misspelled.

Second, the sentence could read: 

"According to a recent study, respiratory conditions are a major cause of disability and consequent retirement of city firefighters, in the seven years following 9/11."

Main Entry: account for  

Part of Speech:  verb

Definition:  give reason for

Synonyms:  clarify, elucidate, explain, justify, resolve

Additional corrections are required to your sentence.

It is either "Recent studies found ..." or "A recent study found ..." No commas are needed following disability and firefighters.

I'm sorry Rahul, but "reported" does not make sense as a replacement for "accounted for".  Instead, "reported" could replace "found". 

In some ways, "accounted for" may be your best choice. Here are some alternates (note I've added claims and early to clarify your sentence).

A recent study found that respiratory conditions represented the large share of disability claims and early retirements among city firefighters...

A recent study found that respiratory conditions caused the largest share of disability claims and early retirements among city firefighters...

A recent study found that respiratory conditions were behind the largest share of disability claims and early retirements among city firefighters...

I hope this helps.

Or you can rework the section.    I think accounted for is quite appropriate.  

A recent study found that respiratory conditions accounted for most of the disabilities and retirements among city firefighters in the seven years following 9/11.

The checker doesn't like me using "the" before disabilities.  I tend to agree with Jeff above.