## 1 Introduction  
The marine environment is highly exposed to natural compounds and anthropogenic products and chemicals that are released daily and/or accidentally [1; 2; 3]. Coastal areas, including intertidal/supratidal zones, are highly polluted even though they are important in marine ecosystems and provide reproduction zones for the larval growth of many species. This critical issue is prevalent in many coastal areas globally [1; 4; 5]. A wide variety of pollutants is present, such as pesticides [6], antibiotics [7], polycyclic aromatic hydrocarbons [8], heavy metals, and persistent organic pollutants. These environmental pollutants affect and disrupt marine ecosystems, and biomonitoring is necessary to understand these environmental issues. Heavy metal pollution is widespread and is studied traditionally in the field of environmental pollution. Researchers have focused on several highly toxic elements, such as cadmium (Cd), chromium (Cr), mercury, selenium, lead (Pb), arsenic, fluorine, and boron. These toxic heavy metals can be released from natural sources [9; 10; 11] and can be discharged from anthropogenic sources, such as industrial activity [12; 13]. Mining provides one of the sources of heavy metals of most concern [14; 15]. In the 1910s-1970s, wastewater that contained Cd was released from a mining area in Toyama, Japan, into a surrounding river. The release resulted in a severe health disease, known as \"Itai-titai disease\", and soil contamination [16; 17]. Some heavy metals are essential to organisms, but excess amounts cause health issues [18; 19]. Heavy metals tend to be detected in aquatic wildlife, fish [20], mussels [21; 22], sea mammals [23], and isopods [24; 25; 26; 27]. Dioxins, including 75 polychlorinated dibenzo-\(p\)-dioxins (PCDDs), 135 polychlorinated dibenzofurans (PCDFs), and 12 dioxin-like polychlorinated biphenyls (DL-PCBs), are one of the most known persistent organic pollutant categories that have been regulated by the Stockholm Convention since 2001. These compounds are of great concern as marine wildlife [28; 29] and human [30; 31] environmental pollutants. These pollutants are ubiquitous marine environmental pollutants globally and have even been detected in polar areas [32; 33]. The PCDD/F and DL-PCB toxicity depends on each congener chemical structure. The World Health Organization established the \"Toxic Equivalency Factor (TEF)\", which sets 2,3,7,8-TCDD as the highest toxic dioxin to 1 and converts the toxicity of each dioxin compound as a relative value to assess the total dioxin toxicity (toxic equivalent, TEQ) in 2005. These dioxins are generated as byproducts from the incomplete combustion of substances that contain carbon, oxygen, hydrogen, and chlorine. Due to their high hydrophobicity (water octanol partition coefficient, log Pow: 6.3-8.2), dioxins are highly accumulated in organisms. However, a few studies have reported environmental pollution with these pollutants, especially PCDD/Fs and DL-PCBs, using organisms' habitats in the supratidal zone around Japan. Environmental surveys of coastal areas tend to focus on intertidal zones and use mussels for biomonitoring [4; 34; 35]. Scientific effort has been expended over several decades to accumulate numerous baseline data. Environmental pollution with many compounds is thought to be distributed in the broad range of coastal areas, including intertidal and supratidal zones [8; 36; 37]. Environmental research conducted to date has focused mainly on the intertidal zone. One of the most difficult survey points in supratidal zones is the selection of suitable biomonitoring species. To address this scientific gap, our research group used the wharf roach _Ligia_ spp. as an environmental biomonitoring species. Wharf roaches have a global distribution in temperate-tropical areas [38], occur in relatively small habitat areas [39], are omnivorous [40], and may be exposed to environmental pollutants via feeding in land above the tidal line.