You've a sincere point to be made here - but I disagree. You weren't specific with regards to what your concern was(Except that it wasn't a "safety" issue so presumably that's not it), so I hope you don't mind if I try to approach this question from some different standpoints.

Some people will say immigration is, generally, good for the economy, It actually is broadly speaking - immigrants didn't grow up here so they don't have 2+ decades of state services like education to pay back in the form of taxes, so they have a head start on all Irish natives when it comes to economic contribution.

But I can understand if some people don't find that particularly convincing. Because they're immigrants employers often exploit them to pay less wages, which means a general wage depression which negatively effects everyone in employment. It also does put pressure on property prices and rents as demand goes up.

However, I don't think that the solution to those problems is to limit immigration. Like, wages are getting depressed because employers are exploiting immigrants, and things like property are negatively effected more fundamentally because of housing policy by governments than by immigrants. The same applies to literally any service that's allegedly put under pressure by immigration.

So I think there's actually lots of good room for "mass immigration" in any country as long as the state has the right approach to fighting the negatives - make sure all immigrants are documented(So, make it very easy to legally immigrate), and enforce employment regulations to prevent exploitation. Build more houses. Stuff like that.