The unhealthy vitamin
Concern has also been raised as to whether injections of vitamin K given immediately after birth increase the risk of childhood cancer. In 1990, a positive association was found between the vitamin K jab and childhood leukaemia. The study involved 597 children in England and Wales born between 1968 and 1985, and diagnosed with cancer between 1969 and 1986, and a matching group of children who didn’t have cancer.
The association between overall cancer incidence and intramuscular vitamin K was small. However, there was a strong association with the incidence of leukaemia. The authors concluded that '. . . the risk, if any, attributable to the use of vitamin K cannot be large, but the possibility that there is some risk cannot be excluded' (Br J Cancer, 1990; 62: 304-8).
Eight years and a great deal of debate later, the British Medical Journal devoted an entire issue to vitamin K injections and its link with cancer. An editorial likened the subject to a 'Gordian knot' that still awaits untying (BMJ, 1998; 316: 161-2). One of the studies found no association (BMJ, 1998; 316: 184-9), but others felt otherwise. 'The possibility that there is some risk cannot be excluded,' concluded one (BMJ, 1998; 316: 178-84).
A third study looking at British children who developed cancer before age 15 found no association between intramuscular vitamin K and all childhood cancers and leukaemia. But once again, there was a raised risk for leukaemia developing one to six years after birth.
The researchers concluded, 'It is not possible, on the basis of currently published evidence, to refute the suggestion that neonatal intramuscular vitamin K administration increases the risk of early childhood leukaemia' (BMJ, 1998; 316: 189-93). The most recent review of the vitamin K-cancer link arrived at much the same conclusion (Br J Cancer, 2002; 86: 63-9).
Are kids electric?
Evidence is also accumulating to show that living near even relatively low levels of electromagnetic field (EMF) radiation from mains electricity or powerlines can significantly raise a child’s chances of developing leukaemia. In 1979, the first major study linking such EMFs to childhood cancer was published (Am J Epidemiol, 1979; 109: 273-84).
Other studies followed, including a Swedish study of some half a million people showing that children exposed to varying levels of household EMFs had up to a fourfold greater risk of developing leukaemia (Am J Epidemiol, 1993; 138: 467-81). Others have also confirmed the EMF-cancer link (Eur J Cancer, 1995; 31A: 2035-9; Lancet, 1993; 342: 1295-6; Am J Epidemiol, 1991; 134: 923-7; Am J Epidemiol, 1988; 128: 21-38).
Most recently, however, back-to-back UK studies on electrical powerlines and cancer reached mixed conclusions. One, by Professor Denis Henshaw of Bristol University’s Human Radiation Effects Group, took 2000 field measurements and found that the toxic effects of EMFs could extend up to more than 100 yards (91 metres) on either side of powerlines.
He also suggested how EMFs could cause cancer. According to Henshaw, living near powerlines with radiation levels dozens of times the legal limit may indirectly cause cancer by increasing the concentration of carcinogenic airborne particles that are produced naturally in the soil and by local traffic pollution (Int J Radiat Biol, 1999; 75: 1505-21). This conclusion supports earlier research showing potentially toxic interactions between alternating EMFs surrounding powerlines and radioactive breakdown products of naturally occurring radon gas (Int J Radiat Biol, 1996; 69: 25-38).