In the half-century since a ruinous war of independence, Bangladesh has emerged as an often unheralded economic success story, overtaking its neighbour India in terms of per capita income. But environmentalists say that growth has come at a terrible cost, with a toxic melange of dyes, tanning acids and other dangerous chemicals making their way into the country's rivers, creating long-term environmental damage and serious health problems for the population. IMAGES AND SOUNDBITES ARRANGED IN SEQUENCES