We all think of the womb as a safe haven possibly the only one we will enjoy in our lifetime but there are warning signs from a range of studies to suggest that the unborn child will face 'prenatal pollution' from toxic chemicals even there.
One significant marker of early pollution, and particularly from polychlorinated chemicals, is the development of teeth. Dentists from Finland have been studying how these chemicals interfere with tooth development since the early 1980s. They noticed that many children had poorly developed molars, which were discoloured and soft. The normal hard enamel was missing, making the teeth more readily subject to decay.
They made the connection to prenatal pollution after children in Taiwan, whose mothers while pregnant were exposed to dioxins, displayed similar tooth problems. The Finnish dentists experimented with rats and found that exposure to the most toxic dioxin-tetrachlorodibenzo-p-dioxin (TCDD) leads to developmental defects of dental hard tissues (Toxicology, 1993; 8: 1-13).
To find out whether teeth could be used as a biomarker of exposure to polychlorinated chemicals, they examined the dentition of 102 children, aged between six and seven, for the presence of hypomineralised enamel defects (Lancet, 1999; 353: 206).
The permanent first molars were the target teeth. The degree of early pollution was estimated by measuring concentrations of the most toxic polychlorinated dioxin/furan and 33 biphenyl congeners in milk samples collected when the child was aged 4 weeks.
Hypomineralised enamel defects were seen in the first molars of 17 children. Severity varied from chalky lesions to localised loss of enamel associated with affected dentine. Mineralisation defects occurred more often and were most severe in children who had been exposed to higher amounts of polychlorinated chemicals.
The researchers concluded that hypomineralised dental defects may be the best available indicator of dioxin exposure. Defects are seen after exposure to very low concentrations and such defects can be diagnosed even after many years.
But there are other factors that can also suggest prenatal pollution. A Dutch study that looked at the neurological development of 418 children at the age of 18 months found that exposure to PCBs in the fetus had a negative influence on the neurological condition. Interestingly, no negative effects of exposure to PCBs and dioxins through breast milk could be detected. On the contrary, breast milk had a significant positive effect on the fluency of movements (Early Hum Dev, 1995; 43: 165-76).
Similar conclusions can be drawn from an American study of the intellectual functions of 11 year old children. The researchers recruited 212 newborns born to mothers who had eaten Lake Michigan fish contaminated with PCBs. Concentrations of
PCBs in maternal serum and milk at delivery were slightly higher than in the general population. Prenatal exposure was evaluated by measuring concentrations in umbilical cord serum and by taking into account maternal serum and milk concentrations.
When the children reached the age of 11, a battery of IQ and achievement tests was given. Prenatal exposure to PCBs was associated with lower IQ scores after control for potential confounding variables, such as socioeconomic status. The strongest effects were related to memory and attention. The most highly exposed children were three times as likely to have low average scores and twice as likely to be at least two years behind in reading comprehension. Although larger quantities of PCBs are transferred by breastfeeding than in utero, there were only deficits in association with transplacental exposure (N Engl J Med, 1996; 335: 783-9).
Another concern is the increase in disorders of the male genital tract. Reports in different industrialised countries indicate that more and more boys have undescended testicles. A Spanish study compared the rate of undescended testicles, or cryptorchidism, in the different regions of Granada. Fruit and vegetable crops in the province are treated with 51 per cent of the pesticides used in Spain. In much of the area along the Mediterranean coast, greenhouse crop farming under plasticencased networks is widespread. In the enclosed greenhouses, workers including pregnant women are exposed to high levels of pesticides. It was found that rates of operations for undescended testicles were significantly higher in areas where pesticide use was high sometimes more than twice the rate of other areas (Environ Health Perspect, 1996; 104: 394-9).
Pollution has been cited as the most likely cause for the increase in birth defects, which has been noted in a study conducted by the Centers for Disease Control in the USA. During the study period, from 1989 to 1996, preterm births rose by 4.5 per cent among white women, and the rate was even higher among African American women.
Finally, we are also witnessing in industrial countries a decline in the number of male births over the past three decades. Denmark, the Netherlands, Canada, the USA and some Latin American countries have all reported a decline, as have Finland and Italy.
Although the explanation for this decline may be multifactorial, it is highly probable that prenatal pollution is the main cause. It also seems likely that we will soon be seeing many more similar warning studies.
!ADr Michel Odent
Michel Odent, a pioneer of water and natural birth, runs the Primal Health Research, from whose winter 1999 newsletter this article was adapted. Primal Health Research can be contacted at 59 Roderick Road, London NW3 2NP.