Technological developments have dramatically reduced mortality resulting from many diseases. In many instances, however, disease incidence is increasing, although for some conditions without standardized tracking mechanisms, trends are difficult to determine accurately. The burden from current patterns of disease and disability is enormous and extracts a terrible toll from individuals, families, and communities. Nearly 12 million children in the U.S (17 percent) suffer from one or more developmental disabilities, including deafness, blindness, epilepsy, speech defects, cerebral palsy, delays in growth and development, behavioral problems, or learning disabilities. Learning disabilities alone affect 5 to 10 percent of children in public schools, and these numbers appear to be increasing.
Small exposures to substances like lead, mercury, or polychlorinated biphenyls (PCBs), which have no discernible impact on adults, can permanently damage the developing brain of a child, if the exposure occurs during a window of vulnerability. Early exposures to dioxin or polychlorinated biphenyls (PCBs), chemicals from industrial activities that bioaccumulate in dietary fat, damage the developing immune system, making the child more prone to infections. Risks of asthma and high blood pressure are increased by early environmental exposures. Recent research from Sweden concludes not only that environmental factors play a more important role than genetic inheritance in the origin of most cancers, but also that cancer risk is largely established during the first 20 years of life.
Attention deficit hyperactivity disorder conservatively affects 3 to 6 percent of all school children, and the numbers may be considerably higher. The incidence of autism seems to be increasing, though much of this apparent increase may be due to increased reporting. The age-adjusted incidence of melanoma, lung (female), prostate, liver, non-Hodgkin’s lymphoma, testis, thyroid, kidney, breast, brain, esophagus, and bladder cancers has steadily increased over the past 25 years. Some birth defects, including disorders of the male reproductive system and some forms of congenital heart disease, are increasingly common. Sperm counts and fertility are in decline in some areas of the U.S. and other parts of the world. Asthma is more common and more severe than ever before.
Genetic factors explain far less than half of the population variance for most of these conditions. Although smoking and sun exposure are well-recognized risk factors for some conditions, improved understanding of development of the brain and the immune, reproductive, respiratory, and cardiovascular systems leads to the conclusion that other environmental factors play a major role in determining current patterns of disease.
Infants of mothers who smoke may receive greater exposure to the products of tobacco smoke through breast milk than through environmental exposure, according to a study led by researchers at the Massachusetts General Hospital (MGH) and Brigham and Women’s Hospital (BWH). The study showed a 10-Fold Increase Over Environmental Exposure Alone According to the report appearing in the June issue of the American Journal of Public Health, urine levels of cotinine, a substance produced by the breakdown of nicotine in the body, were 10 times higher in breast-fed children of smoking mothers than in bottle-fed children of smoking mothers.
Maria A. Mascola, MD, MPH, first author of the study says, “While we don’t know for sure whether the compounds present in breast milk are related to any of the harmful health effects seen in some children of smoking women—from reduced lung function to greater incidence of asthma and other illnesses—this does stress how important it is to help mothers refrain from smoking both during pregnancy and while they are nursing.” Mascola is director of Perinatal Epidemiology in the Vincent Obstetrics and Gynecology Service at the MGH.
This investigation was part of the Maternal/Infant Lung Study, a long-term project conducted by the Channing Laboratories at BWH in collaboration with the East Boston Neighborhood Health Center. The researchers examined data from 330 mother/infant pairs who received prenatal, obstetric and pediatric care through the East Boston Center, analyzing information about maternal smoking and the presence of other smokers in the home along with results of urine tests taken from the infants in the first year of life. While cotinine, the substance tested for, is not known to have any harmful effects itself, it is generally used as a marker for the presence of nicotine and other tobacco products.
As expected, cotinine levels in bottle-fed infants of smoking mothers were about eight times higher than in bottle-fed infants of non-smoking mothers. But among children of smoking mothers, infants who were breast-fed had cotinine levels ten times higher than those of bottle-fed infants. Type of feeding had no effect on the cotinine levels of infants of non-smoking mothers.The researchers also found significantly higher cotinine levels in infants of non-smoking mothers who were exposed to tobaccco through smoking by another household member, with no difference related to feeding. For infants of smoking mothers, the presence of another smoker in the household caused a small, statistically insignificant increase in cotinine. In addition, children of mothers who smoked in the same room as their infants also had a small, statistically insignificant increase in cotinine over children of mothers who always smoked in rooms away from their infants.
“Our 10-year study has looked at a lot of factors related to the ways kids can be exposed to tobacco smoke on a prenatal and postnatal level,” says John P. Hanrahan, MD, MPH, of the respiratory epidemiology section at Channing Laboratories and BWH, the study’s senior author. “A lot of people have assumed that the inhalation of passive smoke is totally responsible for the adverse health effects seen in children of smoking mothers. This study has widened our view of the ways smoking may be detrimental to the health of children.”
What are we doing to protect our children?