Globally, 7-10 billion tonnes of waste are produced annually1,2, including 300-500 million tonnes of hazardous wastes (HW) --explosive, inflammable, toxic, corrosive, and infective ones3,4. About 10%5 of these HW are traded through a world-wide waste web (W4). The volume of HW traded through the W4 in the last 30 years has grown by 500%6 and will continue to grow7, creating serious legal8, economic6, environmental9 and health10 problems at global scale. Here we investigate the tip of the iceberg of the W4 by studying networks of 108 categories of wastes traded among 163 countries in the period 2003-2009. Although, most of the HW were traded between developed nations, a disproportionate asymmetry existed in the flow of waste from developed to developing countries. Using a dynamical model we simulate how waste congestion propagates through the W4. We identify 32 countries with poor environmental performance which are at high risk of waste congestion. Therefore, they are a threat of improper handling and disposal of HW. We found contamination by heavy metals (HM), by volatile organic compounds (VOC) and/or by persistent organic pollutants (POP), which were used as chemical fingerprints (CF) of the improper handling of HW in 94% of these countries.