Paul Winchester, MD, reports his findings today at the Pediatric Academic Societies' annual meeting in Toronto, Canada, a combined gathering of the American Pediatric Society, the Society for Pediatric Research, the Ambulatory Pediatric Association, and the American Academy of Pediatrics.
'A growing body of evidence suggests that the consequence of prenatal exposure to pesticides and nitrates as well as to other environmental contaminants is detrimental to many outcomes of pregnancy. As a neonatologist, I am seeing a growing number of birth defects, and preterm births, and I think we need to face up to environmental causes,' said Dr. Winchester.
A premature baby is born before the 37th week of pregnancy. Premature birth occurs in between eight to 10 percent of all pregnancies in the United States.
The rate of premature birth in the United States has risen about 30 percent between 1981, when the government began tracking premature births, and 2005, according to the National Center for Health Statistics, a division of the Centers for Disease Control and Prevention.
The prematurity rate was 9.4 in 1981; it has increased every year since then except for slight dips in 1992 and 2000.
Winchester and his colleagues found that preterm birth rates peaked when pesticides and nitrates measurements in surface water were highest, from April through July, and were lowest when nitrates and pesticides were lowest, in August and September.
More than 27 million U.S. live births were studied from 1996-2002. Preterm birth varied from a high of 12.03 percent in June to a low of 10.44 percent in September.
The highest rate of prematurity, 11.91 percent, occurred in May and June and the lowest, 10.79 percent in August and September. These results were independent of maternal age, race, education, marital status, alcohol or cigarette use, or whether the mother was an urban, suburban or rural resident.
Pesticide and nitrate levels in surface water were also highest in May-June and lowest in August and September, according to the U.S. Geological Survey.
'Preterm births in the United States vary month to month in a recurrent and seasonal manner. Pesticides and nitrates similarly vary seasonally in surface water throughout the U.S. Nitrates and pesticides can disrupt endocrine hormones and nitric oxide pathways in the developing fetus,' Winchester said.
Because they are born too early, premature babies weigh much less than full-term babies. They may have health problems because their organs did not have enough time to develop and need special medical care in a neonatal intensive care unit, where they stay until their organ systems can work on their own.
'I believe this work may lay the foundation for some of the most important basic and clinical research, and public health initiatives of our time,' said James Lemons, MD, professor of pediatrics at the IU School of Medicine.
Dr. Lemons is director of the section of neonatal-perinatal medicine at the IU School of Medicine and heads the Riley Hospital for Children of Clarian Health's section of neonatal-perinatal medicine.
'To recognize that what we put into our environment has potential pandemic effects on pregnancy outcome and possibly on child development is a momentous observation, which hopefully will help transform the way humanity cares for its world,' Lemons said.
In young infants, ingestion of nitrates, components of fertilizers that are often washed into surface water and groundwater, can reduce the blood’s ability to carry oxygen.
The association between nitrate-contaminated well water and inability of the blood to carry oxygen was first described by Hunter Comly, an Iowa City physician during the early 1940s.
In 1974, the Safe Drinking Water Act set a maximum contaminant concentration for nitrates of 10-milligram per liter for public water supplies, but it does not apply to private wells.
In a 1994 survey of 5,500 private water supplies in nine Midwestern states, 13 percent of the wells were found to have nitrate concentrations greater than the standard.
The state of Wisconsin is well aware of the problems nitrates in drinking water can cause for premature babies, especially in rural areas. In 2006, the state Department of Natural Resources, DNR, issued a warning that nitrates that are washed into groundwater from fertilizer can be dangerous to infants, and especially to premature infants.
'All infants less than six months of age are at risk of nitrate toxicity, but premature babies and babies with other health problems are more sensitive than healthy infants,' the DNR said.
Well owners are advised that the only way to know if their drinking water contains nitrate is to have a water sample tested by a certified laboratory. Testing is recommended for well water used by pregnant women and is 'essential for a well that serves infants under six months of age,' the DNR says. The DNR provides a list of certified labs online at: dnr.wi.gov/ org/es/science/lc.
The state of Indiana Department of Natural Resources does not address this issue.
For the past four years, Winchester and colleagues have focused attention on the outcomes of pregnancy in Indiana and the United States in relation to environmental pesticides and nitrates in surface and drinking water.
Last year at the Pediatric Academic Societies' annual meeting, Dr. Winchester reported that birth defects peak in Indiana and in the United States as a whole during April through July, the same months as pesticides and nitrates reach their maximum concentrations in surface water. This year's presentation expands upon that work.
Collaborating with Dr. Winchester on this study were Akosua Boadiwaa Adu-Boahene and Sarah Kosten of the IU School of Medicine, Alex Williamson of the U.S. Geological Survey, and Ying Jun, PhD of the University of Cincinnati.
The work was funded by the Division of Neonatology, Department of Pediatrics of the IU School of Medicine.