It is intellectually dishonest to just say it is not possible for anything to leak and have adverse effects on people without actively researching the matter.
Both gases are inert, so they really don't do anything else. There isn't anything to investigate here.
Are people really so scientifically illiterate that they immediately assume that if anything goes wrong with a complicated machine that it will be harmful to their health?
But the beam never colides with the gas deposits. The helium and nitrogen are used to cool the magnets that are used to bend the beam that travels inside a vacuum tube.
[And even if the beam colides with the gas deposits, I don't expect too much radioactive waste. Each particle in the beam has a lot of energy, but there are very few. This links https://public-archive.web.cern.ch/en/lhc/Facts-en.html says "trillions" ( 10^12 ?) of protons, but a glass of water has like 10^26 protons. A nuclear power plant has much more radioactive material and during normal operation produce much more collisions that can turn container radioactive.]
This one is giving me a headache.
Effects on the local population? You mean those who work there underground? Their voice may change pitch a little, but its only a temporary effect.
Helium is present in our atmosphere. And presumably on your birthday party when a balloon was popped.
Effects on the wider population?
A couple of delays and reorganizations at the surrounding hotels and restaurants.
Basically: the telephone will ring.
Safety is an important part of the collaboration, which is evident when you work there.
This is evaluated by people who understand physics, chemistry, and biology, and it is the alternative science people that tend to not want to believe that and keep warning of dangers that don't exist.
It is good to always remain critical, but after a while you've used up all arguments to explain that the radiation in your microwave is not radioactive.
I guess the scary part is that they called it a leak instead of a hole. I am sure if I say there is a leak in my sock that some will start to worry.
This isn't an argument. 70 years ago France was conducting atmospheric nuclear tests that caused people and inhabited land to be exposed radioactive fallout.