Editor, The News:

In addition to what John Musser, spokesman for Dow Chemical Co., said in his ''Midland Issues'' letter -- ''Dow responding well to dioxin challenges'' -- I would like to add what the World Health Organization said about dioxins.

As late as November 2007, WHO states that dioxins are definitely harmful environmental pollutants. They have the dubious distinction of belonging to the ''dirty dozen'' -- a group of dangerous chemicals known as ''persistent organic pollutants.''

WHO says ''short-term exposure of humans to high levels of dioxins may result in skin lesions, such as chloracne and patchy darkening of the skin, and altered liver functions. Long-term exposure is linked to impairment of the immune system, the developing nervous system, and the endocrine and reproductive functions. Chronic exposure of animals to dioxin has resulted in several types of cancer.''

Furthermore, WHO's International Agency for Research on Cancer has classified the TCDD dioxin species (2,3,7,8-tetrachlorodibenzo para dioxin) as a ''known human carcinogen.''

Now is the time for Dow to complete the job of cleaning up its dioxins.

Richard A. Maltby