Farm-raised salmon contain significantly more dioxins and other potentially cancer-causing pollutants than do salmon caught in the wild, says a major study that tested contaminants in fish bought around the world and was funded by the Pew Charitable Trusts.

Salmon farmed in Northern Europe had the most contaminants, followed by North America and Chile, according to the study released Thursday. It blames the feed used on fish farms for concentrating the ocean pollutants.

Eating more than a meal of farm-raised salmon per month, depending on its country of origin, could slightly increase the risk of getting cancer later in life, researchers conclude.