I found this information in the NY times. Here is the article:

NATIONAL DESK | June 15, 2001, Friday

Vitamin C Pills Tied to DNA Risk

( AP ) 367 words
Late Edition - Final , Section A , Page 26 , Column 1

ABSTRACT - University of Pennsylvania study led by Ian C Blair finds that vitamin C pills that millions of health-conscious Americans take may actually help produce poisons that can damage DNA, a step toward forming cancer cells; findings do not mean that vitamin C causes cancer, but does sound warning about use of vitamin C pills; study is published in journal Science (S)

I did not read the original article.

Here is the original article:

Science 2001 Jun 15;292(5524):2083-6 (ISSN: 0036-8075)
Lee SH; Oe T; Blair IA
Center for Cancer Pharmacology, University of Pennsylvania, 1254 BRB II/III, 421 Curie Boulevard, Philadelphia, PA 19104-6160, USA.