The phrase 'insidious impact' is correct and usable in written English.
You can use it to describe a negative effect that is not obvious or easy to detect, one that accumulates gradually over time. For example, "The insidious impact of pollution on the environment is slowly wreaking havoc on birds and other wildlife."
Maybe it illuminates the pervasive, insidious impact of college ready.
Worse, he believes that corruption has an insidious impact on political institutions and democracy itself.
Fear may have an even more insidious impact than fatigue on performance.
For the most vulnerable nations on Earth, Trump's election has had a little recognised, but insidious impact.
A man, above all else, whose passion never tired and was never defeated by culture, language or ultimately by the insidious impact of money on the sport.
That's the simple truth, and far from you being self-indulgent, it's a crime renowned for its insidious impact on its victims.
… Military leaders in South Carolina came to the microphones of Mr. Graham's events, speaking of "insidious" impacts and "devastating blows".
This responsibility goes beyond the impacts of environmental pollution and other high-profile health issues: there are also the more insidious impacts of tobacco, sedentary lifestyles, overconsumption of foods high in fat, sugar and salt, and unhealthy workplaces and working practices.
Too many are carried, too many are used, always with devastating effect on individual victims and with insidious, corrosive impact on the wellbeing of the local community".
Socially and institutionally we find it hard to acknowledge the historical legacy and the insidious, invidious impact of racism because it quickly descends into a blame game.
"For us to begin reducing the infection rates of HIV in the region, we have to make people aware of how insidious its impact is on the lives of children".
