Answer to Question #8147 Submitted to "Ask the Experts"

Q

I have a 4 1/2-year-old son. He was born in Joliet, Illinois. Joliet, Illinois, has high levels of radium in the drinking water. The year he was born the levels of all of the different wells were at anywhere between 10 pCi/L and 24 pCi/L—I was told the water is combined from many different wells. At the time of my pregnancy and during the first year of his life (I breastfed for 11 months) I ingested this water. I tried to drink two liters per day because that is what I was supposed to do while pregnant and breastfeeding. We had a little carbon filter on our faucet, but that is the only form of filtration we used (I have since read that carbon filters are bad because they can trap radium and it can leach out over time). Anyway, I am now concerned about my son's risk of developing bone cancer or leukemia because of this water that I drank. Is it true that infants absorb much more radium than adults do—therefore resulting in greater risk to the child? After he turned one year old we began to use a reverse osmosis filtration system.

A

In the 1950s there was considerable interest in radium in drinking water in Illinois because of the finding of relatively high concentrations compared with other water supplies in the United States. There are several publications showing the range of radium concentration in drinking water in Joliet, Illinois, to be from 1 to 25 pCi/L, with an average of about 6 pCi/L.

Radium is similar to calcium in its body metabolism and most radium goes directly to bone, with just a small percentage remaining in other tissues. Because of its close association with calcium, radium in bone is reported as a ratio of radium to calcium (pCi radium/gram calcium).

The placenta does not discriminate against radium; that is, it is absorbed the same as calcium. In a very large study of radium in the skeleton as a function of age, the fetal skeleton had the same ratio of radium to calcium as children and adults.

Radium in the body is excreted very efficiently and the amount in the body is equal to about 25 days of intake. An estimate of the annual dose from ingesting even unfiltered water at 25 pCi/L and two liters per day is 20 millirem (0.02 rem). This is five percent of the annual dose from other natural background radionuclides.

Children are not at higher risk for bone cancer than adults; thus the calculated risk is very small based on radiation dose. However, of more importance is the fact that bone cancer from radium exposure is the only radiation exposure known to have a threshold, with bone cancer seen only for doses greater than about 1,000 rem.

I hope this answers your concerns.

Naomi Harley, PhD
Professor, New York University Medical School