According to a new government survey of coastal waters in California, USA, 19% of those sampled contained fish with exceeding high mercury and PCB levels, which is especially dangerous for children and expectant mothers, as consuming these toxic substances can cause nervous system damage, cancer and reproductive harm.

http://news.xinhuanet.com/english2010/world/2011-05/30/c_13900126.htm
http://www.huffingtonpost.com/2011/05/29/mercury-pcbs-widespread-i_n_868657.html
http://www.sacbee.com/2011/05/28/3661713/mercury-pcbs-widespread-in-sport.html