The phrase "are probably harmful" is correct and usable in written English.
It can be used when discussing potential negative effects or risks associated with a subject or action.
Example: "These chemicals, if ingested, are probably harmful to human health."
Alternatives: "may be detrimental" or "could be harmful."
I think it's probably harmful".
"I think President Putin represents a deep strain in Russia that is probably harmful to Russia over the long term, but in the short term can be politically popular at home and very troublesome abroad," he added.
President Obama said (to the Economist) last August: "Russia I think has always had a Janus-like quality, both looking east and west, and I think President Putin represents a deep strain in Russia that is probably harmful to Russia over the long term….But I do think it's important to keep perspective".
Overall, about 62% of responders stated that secondhand smoking was definitely harmful and, when combined with the 30.7% who stated that it was probably harmful, the proportion rose to 92%.
The GYTS data show that the adolescents surveyed are well aware of the unhealthy effects of smoking: 85% of both males and females stated that smoking was definitely harmful and, when combined with those who stated it was probably harmful, the proportion rose to 97%.
With all of the aforementioned studies in mind, the results provided by the Alberta Sepsis Network investigators provide additional evidence that overly aggressive fluid resuscitation in critically ill children with severe sepsis/septic shock is not only unlikely to be helpful, but also is probably harmful.
It is thought that trace amounts in drinking water are probably not harmful.
What's more, they point out, customers ought to be aware that toxins from untreated fungal disease are probably more harmful than pesticide residues are, and that plants themselves produce chemicals designed to protect them against pests.
I'm open-minded about omega-3 and vitamin D because there is emerging data showing these may be beneficial and are probably not harmful.
Electronic cigarettes are probably less harmful than tobacco smoking, but they are almost certainly more dangerous than medicinal nicotine inhalers [ 6, 7].
