I was heartened to see Juan Williams call attention {Outlook, Dec. 30} to the evidence that babies born exposed to drugs do not necessarily face permanent damage from the drugs themselves. The other side of Mr. Williams' story, however -- that babies born to crack addicts do face permanent damage from growing up in uncaring, drug-riddled environments -- raises critical questions our child welfare system must address.

There is no question that biological parents are the first and best resource for raising children successfully. And in those cases where poverty, unemployment and other such pressures cause families to break down, family preservation services can often succeed at keeping biological families together.

But The Post errs in editorializing {"Saving Children," Jan. 2} that increased funding for family preservation services is the District's best bet for improving the lives of its neediest children. It is an appalling modern reality that parents who abuse drugs -- especially crack -- are often both incompetent at and uninterested in raising their children. In those sad cases where drugs have made a travesty of the very notion of family, it is essential that judges and social workers insist on the immediate removal of children from their parents' custody. Children must not be allowed to stay in hard-core drug environments that can, as Mr. Williams points out, damage them for life.

As a result of efforts to teach the public about AIDS, it appears to be easier now to find foster parents for children with AIDS than it is to find ones willing to care for babies born exposed to drugs. Mr. Williams has done a great service by pointing out that, given loving homes and appropriate therapy, children born exposed to drugs have a good chance to grow up healthy and happy. As more people hear the hopeful news about drug-exposed babies, chances are that more will come forward to give them homes.

No one would dispute that it's tough to decide whether to try to preserve a family or remove a child from his or her parents. In those cases where such calls have to be made, however, it is the responsibility of those involved to put the children first. Depending on the situation, that might call for family preservation, temporary foster care or a group home, or it might call for termination of parental rights and adoption by a loving family. In any case, we must think of the children first -- not just for their sake but for the sake of our society and its future.

MARY SHEILA GALL Assistant Secretary For Human Development Services U.S. Department of Health and Human Services Washington