Babies exposed to lotion, shampoo and powder had more than four times the level of phthalates in their urine as those whose parents had not used the products. Previous research found that the substances altered the children's hormones.

Infants and toddlers exposed to baby lotions, shampoos and powders carry high concentrations of hormone-altering chemicals in their bodies that might have reproductive effects, according to a new scientific study of babies born in Los Angeles and two other U.S. cities.

The research, to be published today in the medical journal Pediatrics, found that as the use of baby care products rose, so did the concentration of phthalates, which are used in many fragrances.

The lead scientist in the study, Dr. Sheela Sathyanarayana of the University of Washington's Department of Pediatrics, said the findings suggested that many baby care products contain a variety of phthalates that enter children's bodies through their skin.

Manufacturers do not list phthalates as ingredients on labels, so it is unknown which products contain them.

The researchers at the University of Washington and the University of Rochester stressed that the potential effects on babies were uncertain.

But previous animal and human research suggests that early exposure to some phthalates could reduce testosterone and alter reproductive organs, particularly in males.

The three phthalate compounds found in the highest concentrations in babies in the study were linked to reduced testosterone in a 2006 study of newborns in Denmark.

Some scientists theorize such changes in hormones could lead to fertility problems and male reproductive disorders.

Representatives of the fragrance and cosmetics industries said they were surprised by the findings and questioned their validity. They said only one phthalate compound is used in baby products, and it is found in such low levels that they doubt it could explain high concentrations found in the babies.

In the study, doctors tested the urine of 163 children between the ages of 2 months and 28 months born in Los Angeles, Minneapolis and Columbia, Mo., between 2000 and 2005. All had detectable amounts of at least one type of phthalate, and more than 80% had seven or more types.

"Phthalate exposure is widespread and variable in infants. We found that mothers' reported use of infant lotion, infant powder and shampoo was significantly associated with . . . urinary concentrations," the scientists wrote in the new study.

In the study, babies exposed to baby lotion, shampoo and powder had more than four times the level of phthalates in their urine than babies whose parents had not used the products. The highest levels were reported in babies under 8 months old, and those exposed to lotions.

Previous studies have focused on a different route of exposure for children: sucking on soft, vinyl toys. Phthalates, in addition to helping cosmetics retain fragrance and color, are used as plasticizers in some vinyl. A recently passed California law will ban six types in children's toys and feeding products, beginning next year. But no federal or state law in the United States prohibits their use in personal care products or cosmetics.

The study is the first to report that skin transfer may be a main route of exposure for babies.

In their report, the scientists advised parents who want to reduce their baby's exposure to stop using lotions and powders unless their doctors recommend them for medical reasons. They also suggested limiting use of shampoos and other products. Many adult lotions and other personal care products also contain phthalates.

John Bailey, chief scientist for the Personal Care Products Council, an industry trade group, said diethyl phthalate, or DEP, is used in the fragrances of some baby lotions and other baby products.

But DEP is used at "very low levels, in the part-per-million range, below what could possibly account for the levels they are finding" in the babies' urine, Bailey said. "All of the other phthalates, if they're present, have to be coming from someplace else," such as plastics or other products, he said.

Bailey said he couldn't explain why the researchers found such high concentrations in the babies that used lotions and the other products.

But he said the scientists shouldn't have advised parents to stop using them because they did not test any products and cannot prove they were the source.

"The results that are being presented and the conclusions being made don't make a great deal of scientific sense," Bailey said. "There's a lot that makes you question whether their findings are valid."

Europe has banned some phthalates in baby toys and cosmetics, but not the DEP found in fragrances.

More than half the mothers in the new study reported using baby shampoos on their infants within 24 hours of the urine tests, and about one-third had used lotion, and 14% used powder within the same time period.

No link was found to baby wipes or to diaper creams.

The highest concentrations in the babies were for a phthalate known as MEP, which comes from DEP, the compound used in fragrances. One baby had an extremely high level of MEP -- 4.4 parts per million.