Table 8. Mean annual malformation rates (per 1000 total singleton births), 
         1964-66
              All CNS Malformation     Anencephalus Spina bifida    Water     
Area                                                without         hardness
                                                    anencephalus    (p.p.m)

              Non-manual  Manual       Non-  Manual Non-   Manual
                                       manual       manual
Cardiff       4.62 (4 110)8.21 (9 502) 1.22  3.26   2.19   3.47     110
Newport       5.25 (1 523)5.18 (4 634) 0.66  0.65   4.60   3.24     100
Swansea       5.81 (2 408)9.50 (5 579) 3.74  3.41   2.08   5.38     95
Glamorgan 
East Valleys  8.15 (3 189)10.85(13 362) 2.82 4.12   4.39    5.31    42
Glamorgan 
West Valleys  8.02 (1 995)10.15(8 279) 2.51  3.62    5.01   5.31    39
Rest of 
Glamorgan     5.14 (4 863)8.26 (7 868) 2.26  3.18   2.47   3.56     161
Monmouthshire
 Valleys      7.56 (2 380)8.56 (10 048)2.52  3.58    3.36   3.68    83
Rest of 
Monmouthshire 5.58 (1 613)7.50 (3 201) 1.86  2.50    3.72   4.06    122