**3. Environmental and health impacts of dioxine and furan**

PCDD/F and PCB are considered dioxin- and furan-like compounds under Stockholm Convention. PCDDs and PCDFs are unintentional by-products of incomplete combustion process of chlorinated products and known to be widespread and persistent in the environment [3]. 2,3,7,8-tetrachlorodibenzo-*p*-dioxin (TCDD) has been known to be the most toxic congener of all PCDDs and was classified as a carcinogenic 24 substance by WHO's International Agency for Research on Cancer in 1997 [4]. Infants are more sensitive to the exposure of dioxins and dioxin-like compounds such as PCBs. Studies indicated that dioxins and dioxin-like compounds may interfere with thyroid hormone levels, increase risk of growth retardation, delay in developmental landmarks, cause neurocognitive deficits, and lead to reproductive impairments [5–8]. With short-term and high exposure level, TCDD can cause chloracne, a severe skin disease with acne-like lesions on the face and neck, which may also extend to the upper

**Figure 1.** Overview of the human exposure pathways to POPs.

body in human [4]. With acute (14days or less) oral exposure or intermediate (15–364days) and chronic (365days or more) exposure to PCDDs, liver's metabolism, biochemical, and weight change [4]. In Taiwan, several studies were done to determine the effect on children of Yu-Cheng women, who were transplacentally exposed to the pollutants. The results showed that prenatal exposure to PCBs and PCDFs could potentially result in reduced neurocognitive development, hyperpigmented skin and nails, and increased the risk of growth retardation [8]. Furthermore, Guo et al*.* [5] found that prenatal exposure possibly causes deterioration in semen quality, increases the percentage of abnormal sperm, and reduces daily sperm production in sexually matured men who experience in utero exposure.

In recent years, increasing concern has been given to polybrominated congeners of dibenzop-dioxins/furan. Brominated dioxins exert their toxic effects through the same mechanism as- their chlorinated congeners, of which TCDD and its brominated congener 2,3,7,8-tetrabromodibenzo-p-dioxin (TBDD) presented almost identical potencies for the immune toxic effects on- mice [9]. According to the Environmental Health Criteria 205, PBDD/Fs exhibits similar health effects to the animal as their chlorinated congener PCDD/Fs. With the oral exposure of TBDD,- spermatogenic activity decreases and thyroid hormones changes in the Westar rate while- growing retardation and histopathological changes in liver and thymus detects in the Sprague-Dawley rats. However, data on human exposure of PBDD/F are scarce. As it was shown in **Figure 1**, exposure ways of dioxine and furan are diverse. Only limited studies were done on these emerging pollutants, and most of them are concentrated on occupational exposure [4].
