Jan 19 (Reuters) - KGHM Polska Miedz Sa KGH.WA :
* Says will conduct impairment tests aimed at checking the value of its key foreign assets
* Says impairment tests will not include the company's Sierra Gorda asset in Chile
* Says tests stem from significant changes in parameters of some of its mines' lifespan, the volume of metal production, assumed operating costs and the level of capital expenditure during expected lifespan of the mines
Further company coverage: KGH.WA