THE World Wide Fund for Nature Hong Kong (WWF) is launching the territory's first-ever handkerchief campaign to encourage the public to use handkerchiefs rather than tissue paper. WWF handkerchiefs come in two styles, one embroidered with ''WWF'' and the other printed with the WWF panda logo. The simple designs of the handkerchiefs bring out today's trend for more natural and environmental-friendly products. These handkerchiefs will be introduced at a charity sale on June 5, which is World Environment Day. Using handkerchiefs instead of tissue paper will help reduce deforestation and rubbish volume. It will also educate the public, especially youths, to use reusable products. Each two-piece pack of WWF handkerchiefs costs $50. They are available at the WWF headquarters in Tramway Path, the Mai Po Marshes Wildlife Education Centre and Nature Reserve, and the Island House Conservation Studies Centre in Tai Po. Businesses that plan to make group purchases can contact the WWF's Trading Department on 526-1011. A 10 per cent discount with free delivery will be offered to firms that buy over 500 packs. To encourage youngsters under 18 to join its junior membership plan, the WWF will offer those who return five handkerchief packets with a donation of $50 or more, a free membership and an elegant photo frame. Junior members will also receive free subscription to WWF's quarterly publication, Panda Club Post .