July 26 - Doctors once thought that the placenta would shield a fetus from harmful chemicals and pollutants. But new research shows that may not be the case. A study published this month by the Environmental Working Group (EWG), an advocacy group based in Washington DC, found traces of 287 chemicals in the umbilical cord blood of 10 infants. They included mercury, pesticides and the chemicals used in stain-resistant coating and fire-retardant foam. The findings prompted concerns since children’s smaller brains, developing organs and more porous brains put them more at risk from such toxins than adults. "A child's brain is very vulnerable and developing very rapidly in utero and during the first two years of life," says Jane Houlihan, co-author of the study.

While former threats like smallpox and polio are now under control, conditions like autism and asthma are on the rise. Autism rates are up tenfold, asthma cases have doubled and incidences of childhood cancers like leukemia and brain cancer are also high. No one has pinpointed the cause of the increases yet. But reports like this one may leave many parents feeling like they need a PhD in chemistry just to keep their children healthy in an unhealthy, even toxic, world. The EWG study detected perfluorinated chemicals (PFCs), for example, in all 10 of the newborns' blood at a range of 3.37 to 10.7 parts per billion. It's not clear whether chemicals at this ratio can cause cancer or birth defects or precisely what, if any, levels would be safe in such a young population, but these levels are certainly not naturally occurring. The samples also contained up to 14,200 parts per trillion of polybrominate dephenyl ethers (PBDEs), which have been linked to brain and thyroid development problems.

The sample of cord blood in the EWG study is too small to be conclusive.  (There are not many studies of cord blood because it is hard to get and expensive to test.)  But the findings got some support from a comprehensive study of chemicals in Americans' bodies done by the Centers for Disease Control. The report, which came out last week, involved tests of some 2,400 people aged six or older for 62 of the same chemicals, as well as 86 not included in the EWG report. Though levels of lead in children had decreased from previous studies, the report also found some doses of some chemicals in children, including DDE (an industrial pesticide) and phthalates, which are found in nail polish and some plastic toys.

Dr. Lynnette Mazur, who is on the American Academy of Pediatrics environmental health committee, acknowledges that all these studies can be very confusing to parents. "There are a lot of huge names and all these numbers next to them, but there is no clinical correlation with these numbers."  In other words, kids aren't showing up at her office in Houston with obvious effects from pesticide poisoning. But she notes that it takes science awhile to figure out what's going on. "And by then it's usually too late," she says.

That was the case in the coastal town of Minimata in Japan, where residents in the 1940s and 1950s unwittingly ate seafood that had been contaminated with mercury compounds dumped into the bay by a local chemical company. In the early 1950s, residents began suffering brain damage and neurological effects. But it was not until 1959 that researchers realized the victims were suffering the effects of mercury poisoning, and the connection was made to the contaminated seafood and the company that had dumped the waste. 

The mercury found in the infants' blood in the EWG report was not nearly as concentrated as the levels found in Minimata residents. But doctors have long been worrisome about its effects. Pregnant women--and toddlers--are now routinely advised to avoid fish with potentially high mercury content like swordfish, shark and tilefish. These large fish eat little fish that eat the algae that may be contaminated by pollution. Dr. William Weil, who serves on the American Academy of Pediatrician’s Committee on Environmental Health, says he would also put tuna steaks on the list of fish to avoid. Some fish, he says, also accumulate PCBs--industrial pollutants also found in the EWG study--in their fat, but, “the inexpensive canned tuna kids eat is probably safe."

Weil and Mazur aren't alarmists. But they both support the ban-first, study-it-later "precautionary principle," adopted in some countries in Europe when there are any questions about the safety of a chemical. In the United States, it's the opposite scenario: science has to first prove something is harmful before it is banned. The European Parliament, for example, recently banned phthalates. But the Toy Industry Association in the United States scoffed at that move since it says that the risk of phthalates is still being studied. Weil isn't worried about pregnant women using nail polish, but he's concerned about pesticides--especially those used to treat lawns and parks where kids play. "Live with a few dandelions," he says.  He also recommends frequent hand washing. The average two-year-old puts his hands in his mouth nine times an hour, according to Environmental Protection Agency data.  

The good news, and there is some, is that both PCB and lead levels are going down in all age groups. In fact, another study released last week by the Federal Interagency Forum on Child and Family Statistics found that lead levels in children 1 to 5 years old had declined 89 percent since the mid 1970s, when the government took lead out of gasoline after it was found to lower IQs (though lead paint remains a worry). PCBs were also banned in the 1970s, but they linger in the environment for decades. As PCBs are waning, however, PBDEs and PFCs are taking their place and again showed up in the cord blood samples. The first is the chemical in fire retardants; they're often used in furniture foam, for example. So Houlihan recommends that parents should immediately fix any rips that expose the foam. The second is used in stain-resistant clothing and plastic food containers.  To avoid the chemicals, Houlihan suggests parents buy clothes that get dirty and avoid heating food in plastic containers in the microwave. "All this information can seem overwhelming, but there are some simple things that parents can do," she says.