The phrase "a source of major concern" is correct and can be used in written English.
It is typically used to describe a problem or issue that is causing a lot of worry or anxiety. For example: "The rising levels of pollution in the city have been a source of major concern for residents."
As Mr Smithers tartly remarksWe find the current high level of US equities and bonds to be a source of major concern.
Whether the result of individual actions or of a system which is understaffed and under pressure, some of the stories that emerged from Mid Staffs and from our own inquiry, are a source of major concern.
The unmanaged urbanization is also a source of major concern.
Postoperative adhesions have become the most common complication of open or laparoscopic abdominal surgery and a source of major concern because of their potentially dramatic consequences.
Postoperative adhesions fibrous connections developing between tissues and organs as a sequel to surgical trauma have become the commonest complication of open or laparoscopic abdominal surgery and a source of major concern because of their potentially dramatic consequences.
As a means of efficient transferral, they have virtually no impact on the product's processing or specified characteristics, but in the food-processing industry they are a source of major concern for just that reason.
According to a recent paper for the Center for European Reform: "Regardless of the outcome of the presidential election, the euro zone crisis will be a source of major U.S. concern.
Despite the success of current approaches for understanding the PPI network, the large fraction of missing and spurious PPIs and a low coverage of complete PPI network are the sources of major concern.
Several sources should be of major concern: materials treated with ENPs, wastewaters from industrial, hospital, hotel and domestic laundries, as well as the waste produced from all mentioned sources including textiles themselves.
Point sources of pollutants are of major concern in an urban area; on the other hand, non-point sources are of major concern in the rural areas (Asante et al. 2008).
This source of bias is of major concern in cross-sectional and case – control studies of symptomatic OA and may also be a problem in prospective longitudinal studies because patients may have endured gradually increasing joint symptoms for several years before they are diagnosed with primary hip or knee OA.
