its presence in groundwater supply. The USGS concluded that many of the nations aquifers are at risk to low-level VOC contamination. The common symptoms of short levels of exposure to VOCs include headaches, nausea, and eye irritation. If exposed for an extended period of time the symptoms include cancer and damage to the central nervous system. China In an effort to reverse the adverse consequences of air pollution, in 2006, China started to consider a national pollution permit trading system in order to use market-based mechanisms to incentivize companies to cut pollution. This has been based on a previous pilot project called the Industrial emission trading pilot scheme, which was launched in 2002. Four provinces, three municipalities and one business entity was involved in this pilot project (also known as the 4+3+1 project). They are Shandong, Shanxi, Jiangsu, Henan, Shanghai, Tianjin, Liuzhou and China Huaneng Group, a state-owned company in the power industry. This pilot project did not turn into a bigger scale inter-provincial trading system, but it stimulated numerous local trading platforms. In 2014, when the Chinese government started considering a national level pollution permit trading system again, there were more than 20 local pollution permit trading platforms. The Yangtze River Delta region as a whole has also run test trading, but the scale was limited. In the same year, the Chinese government proposed establishing a carbon market, focused on CO2 reduction later in the decade, and it is a separate system from the pollution permit trading. A 2021 study in PNAS found that China's emissions trading system effectively reduced firm emissions despite low carbon prices and infrequent trading. The system reduced total emissions by 16.7% and emission intensity by 9.7%. Europe The EU Emission Trading System was established in the year 2005 - in line with the commitment period of the Kyoto protocol. It follows the cap and trade model where one allowance permits the holder to emit 1 ton of (tCO2). The scheme was said to cover energy and heat generation industries and around 11,186 plants participated in the first stage. These plants only accounted for 45% of all European emissions at the time. More than 90% of all these allowances were free of cost in both periods to build a strong base of abatements for the future phases. This free allocation resulted in the volume and value of allowances growing three-fold over 2006 with the price