Effects of CERN on earth's magnetic field?
CERN is a scientific site developed to create anti matter


The scientific activity at CERN involves many things, anti matter being just one of them. For more information you can read their anti matter page.


  Does this have any negative impact on the environment? 


No. The amount of anti matter is negligible. Any anti matter produced in CERN is also annihilated at CERN as well and does not "escape" outside into the environment. The CERN experiments require lots of power, so there are power plants that have their own environmental impact. There are also people driving and flying to CERN, but those are indirect environmental effects that are not directly due to the experiments.


  Effects of CERN on earth's magnetic field?


CERN has large magnets that are used in their experiments. Their magnetic field is 100,000 times the Earth's magnetic field! But, the magnetic field is constrained to CERN itself and has no effect outside of CERN, and it definitely has no effect on Earth's magnetic field itself.