Parents who have recently adopted a child from China may want to have them tested for kidney damage, according to an Ottawa-based adoption agency.

The Children's Bridge is sending warning letters to adoptive parents following a tainted baby-formula scandal in China that has left four babies dead and more than 50,000 ill.

Although none of the recalled products are believed to have been used by the Children's Bridge agency in China, executive director Sandra Forbes said the organization is warning parents as a precaution.

"We have contacted our on-the-ground people directly in China, and the products used by the child welfare institutes are not on the list," said Forbes, whose organization is the largest international adoption agency in Canada.

None of the adopted children have shown any symptoms of melamine poisoning, Forbes said.

She recommended, however, that adopted Chinese children who may have consumed dairy products in China between December 2007 and August 2008 be tested for kidney damage caused by melamine, a toxic chemical that was added to milk to help boost the appearance of protein.

"Those folks may decide to have their children examined by a pediatrician or tested, given that they really wouldn't know whether their children would have been exposed or not."

Melamine is used in plastics, fertilizers and flame retardants. It has no nutritional value but is high in nitrogen, which makes the products appear to have higher protein content than they actually do. Suppliers to the dairy companies that produced the tainted baby formula have been accused of adding the chemical to watered-down milk.

For families still in the midst of the adoption process, the scandal has been particularly disconcerting.

A Halifax man who is waiting to collect his adoptive eight-month-old daughter, Catherine, has learned her orphanage in China used some of the products suspected of contamination.

"I've heard it can cause kidney stones," said Craig Fraser.

"OK, well what does that mean for a child? Obviously it [can] cause death, so that's the worst case. What if it doesn't cause kidney stones, are there any other impacts? So it's unnerving. We're in kind of a wait-and-see game right now."

Fraser said the orphanage in China has already run some tests that indicate Catherine's health is fine. However, he is still waiting for a second set of test results.

"She's not showing signs, or obvious signs, that she's been harmed by it. That being said, you still want to know for sure."

Fraser said he knows many people who have adopted babies from China, and the concern is growing as the scope of the tainted-milk scandal spreads.

Canadian public health officials said they have yet to find evidence that children living here have been sickened by the contaminated products. Doctors' offices and adoption agencies across the country, however, are reporting a surge in calls from concerned parents.

Canadian adoptions from China peaked in 2005, with about 1,000 babies coming into the country. This year, about 400 babies are expected to arrive.