The Okeo Test is a German consumer reports magazine which began publishing in 1985. Their focus is to test consumer products for harmful chemicals. They also test the usability and overall quality of products.
Specifically with baby slings they tested for harmful finishes such as formaldehyde. They also tested the quality of fabric and usability of the slings. Click here to view the study With sheepskin products, they make sure the skin is free from harmful tanning process residues.
These Eco-tests not only help insure that the products are manufactured in a environmentally friendly manner, but are especially important with products that will be in contact with your sensitive baby.
or 
baby-sling-experts.com a site for ChildrensNeeds
