The main environmental concern that persists in Vietnam today is the legacy of the use of the chemical herbicide Agent Orange, which continues to cause birth defects and many health problems in the Vietnamese population. In the southern and central areas affected most by the chemical's use during the Vietnam War, nearly 4.8 million Vietnamese people have been exposed to it and suffered from its effects. In 2012, approximately 50 years after the war, the US began a US$43 million joint clean-up project in the former chemical storage areas in Vietnam to take place in stages. Following the completion of the first phase in Đà Nẵng in late 2017, the US announced its commitment to clean other sites, especially in the heavily impacted site of Biên Hòa, which is four times larger than the previously treated site, at an estimated cost of $390 million.