In his May 9 letter, Jim Hale, executive director of the Wood Preservative Science Council, described me as "an outspoken environmental activist" who has "a vested interest in speaking out against treated wood."

The facts are:

* As a chemist, professor and author of more than 150 scientific publications, I co-direct a public university environmental research center, the Environmental Quality Institute (EQI) at the University of North Carolina-Asheville, recognized as a leading research center on arsenic in pressure-treated lumber. That is why The Post interviewed me.

* It would have been irresponsible for The Post not to mention that the EQI offers a research survey kit, not sold for profit, that citizens can use to measure arsenic exposure from their decks, play sets or picnic tables. The Environmental Working Group is one of several groups that offer the kit, which is for research and not advocacy.

* My research institute is not allied with any group's policies; it is funded about equally by private companies, government agencies and community and environmental groups.

* Arsenic-treated lumber has now been phased out in the United States, Europe and Japan precisely because it is recognized to be a substantial cancer risk.

RICHARD P. MAAS

Asheville, N.C.