The phrase "a low but persistent" is correct and usable in written English.
It can be used to describe something that is consistently present or ongoing, albeit at a low level or intensity.
Example: "The project faced a low but persistent level of resistance from some team members throughout its development."
Alternatives: "a subtle yet constant" or "a minor yet ongoing".
Ms. Phillips was singing torch songs banked down to a low but persistent simmer, evading melodrama by keeping quiet.
There is a low but persistent level of verbal abuse of identifiably Jewish people on the street.
Ms. Stevens has concluded that "a low but persistent" percentage of the nearly 400,000 people held for deportation each year are citizens.
President Obama has the so-called birthers to contend with; Mr. Cruz, who was born in Canada, is swatting at a low but persistent buzz about whether he's got the right stuff, geographically, to be president.
In this study, we have studied the effect of AAP on rat cortical neurons in culture and report, for the first time, that this widely used drug has a low but persistent toxicity on neurons through a mitochondrial-dependent mechanism involving cyt C release and caspase 3 activation.
In summary, TgS100a8a9 hep mice were characterized by a conditional and tissue-specific transgene expression, which resulted in a low but persistent tgS100a8 and tgS100a9 protein level in the liver under conditions of normal tissue homeostasis.
Anthropogens incite a low level, but persistent immune response to a not-immediately life-threatening situation, which can become dysmetabolic when exposure is chronic.
However, a possibility that this relatively low, but persistent, rate of Ca2+ influx is cytotoxic cannot be presently ruled out.
He had waged what The New York Times described at the time as a "low-key but persistent personal campaign" for a Supreme Court nomination since Nixon was elected in 1968.
It is generally accepted now that chronic heart failure is accompanied by low, but persistent, level of cordiomyocyte death [19].
That maxim has been tested by a low-grade but persistent threat far different than the kind Eakin encountered in Korea: well water that's too dangerous to drink.
