Direct CO_2 emissions from total organic carbon (TOC) in wastewater are often considered to be biogenic,which are not included in the list of carbon emissions. Along with the development of detecting methods,radiocarbon dating (~(14)C) and mass balance of elements reveal that the proportion of fossil carbon (FC) (detergents,cosmetics,pharmaceuticals produced from petrochemicals) in organics of wastewater could reach up to 28% of TOC. As a result, the direct mount of CO_2 generated from FC could take a share of 13% in the total direct CO_2 emissions of TOC, coupled with anaerobic digestion of sludge, the CO_2 emissions could even climb up to 23%. For this reason, the direct CO_2 emission from FC could not be neglected,but should be included in the list of carbon emissions. Thus,if some appropriate sinks for fixing CO_2 from FC could not be found,human beings have to restrain their behavior to a-void excessively exploiting fossil fuels, especially for flammable ice which is still buried underground. Otherwise,the net amount of CO_2 from FC will continuously increase,and thus climate warming will not be avoided.