Average school grade (0-5) Number Mean Median Min Max p All             Children of fishermen 1,776 3.06 3.10 0 4.8 <0.0001 West coast 1,000 3.08 3.10 0 4.8 0.0007 East coast 753 3.04 3.10 0 4.8 <0.0001 Children of referents 6,452 3.16 3.20 0 4.9   Boys Children of fishermen 909 2.89 2.90 0 4.6 0.0003 West coast 517 2.90 2.90 0 4.6 0.01 East coast 383 2.86 2.90 0 4.6 0.003 Children of referents 3,337 2.98 3.00 0 4.9   Girls Children of fishermen 867 3.24 3.30 1.2 4.8 <0.0001 West coast 483 3.27 3.30 1.6 4.8 0.01 East coast 370 3.21 3.20 1.2 4.8 0.0001 Children of referents 3,115 3.35 3.40 0 4.9

Table 4: Average school grade for children of fishermen and children of controls born 1969-1982. Student’s t-test was used to compare children of fishermen (total, west coast and east coast) with children of referents.