Well… your bike likely has several lubricants, and paints as well as coatings that especially in close contact with your skin… especially in the handle bars under friction indeed probably introduce chemicals that will increase some risks, versus never having done it. That is the horror of what we have done with modern material science… Would you prefer a label that gives you only risk increases above say 1% ? Alternatively you can just assume we have complicated the world so much with modern material tech that despite its benefits nearly everything you touch increases your cancer chances in America.