The phrase "are attributable directly" is correct and usable in written English.
It can be used when discussing the direct cause or source of something, often in academic or formal contexts.
Example: "The improvements in productivity are attributable directly to the new training program implemented last quarter."
Alternatives: "can be directly linked to" or "are directly related to".
In 2014, just over 6,700 deaths were attributable directly to H.I.V. Yet it is H.I.V., not the flu, that people dread far more.
Two-thirds of those deaths were attributable directly to Boko Haram; the rest were victims of either side, often caught in the middle.
Thus, virtually all of the tectonic landforms of Asia seem to be attributable, directly or indirectly, to India's collision with Eurasia and its subsequent penetration into the continent.
It would not prevent the obtaining and the use of witnesses and evidence which should be attributable directly to the testimony which he might give under compulsion, and on which he might be convicted, when otherwise, and if he had refused to answer, he could not possibly have been convicted.
Among 500 patients with bacteremia and fungemia, total mortality was 42%; about half of all deaths were attributable directly to infection.
"In 2012, numerous computer systems around the world, including those owned by the US government, continued to be targeted for intrusions, some of which appear to be attributable directly to the Chinese government and military," the report from the US Department of Defense said.
It said the U.S. government has been the target of hacking that appeared to be "attributable directly to the Chinese government and military".
The key to successful indicator development is to precisely define the meaning and specifications of an indicator so that what is being assessed is clear and the assessment of quality is attributable directly to that indicator [ 5, 6, 20].
Because no placebo control group existed in the study, it could not be determined how much of the change from baseline in QOLRAD scores was attributable directly to esomeprazole therapy.
