## 2 Cured-in-Place Pipe  
The CIPP method, first implemented in California in 1976, has gained wide acceptance in sewer rehabilitation processes because of its adaptability to varying pipe geometries and also because it allows for localized repairs. In 1971, [PERSON] developed the first CIPP technique, named \"Insituform\", which was designed to repair a damaged pipe under his London garage without excavation. This technology, wherein resin-saturated fabric tubes were inserted into pipes and cured in place, was first used on Hackney's sewers, and the company Instituform Pipes and Structures Ltd. was formed. Once [PERSON] patented the technology in the U.S. in 1977, the company, Instituform, enjoyed market monopoly until the patent expired in 1994, which sparked competition for the technology [4; 12]. The CIPP process involves the insertion of a resin-impregnated flexible tube into the host pipe, which is then cured with heat or UV light. Its success depends on factors such as pipeline geometry, material compatibility, and the mechanical properties of the materials, including tensile strength and corrosion resistance [13; 14; 15].  
Field exposure measurements sites of CIPP installations in Virginia determined relatively high levels of styrene during installation exceeding maximum contamination levels, although the overall concentrations remained for 44 days post-installation. Aquatic toxicity levels were surpassed, as indicated by algal blooms that can cause fish kills [16]. However, another measurement survey observed no incidence of fish kills. It has been also observed that the styrene concentration decreased by 99% in 20 days showing rapid volatilization [17]. Comparative studies in the issue of dust generation indicated that CIPP emits less Respirable Suspended Particulate Matter (RSPM) than OCPR, even at high temperatures, increased humidity, and higher production rates [18]. A questionnaire on the American Association of Highway and Transportation Officials (AASHTO) committee members in 14 states in the U.S reported that air emissions of styrene during CIPP installations were an issue, with potential impacts on water quality, especially in New York, Virginia, and Oregon [19].  
The studies on Life Cycle Assessment (LCA) have concluded that CIPP has a lower environmental impact than OCPR in 14 out of 18 categories, even when considering reduced input allocations [20; 21]. However, though CIPP is generally considered a greener option compared with OCPR, it also emits harmful VOCs and styrene, which present several risks to human health and the environment [12; 14; 22]. Advanced chemical monitoring techniques like Gas Chromatography-Mass Spectrometry (GC-MS) and Nuclear Magnetic Resonance (NMR) spectroscopy have detected the presence of both styrene and non-styrene compounds. This poses the need for better resin formulations, different post-curing treatments, and more stringent emission controls to the fore [23].  
Field measurements have shown that water-filled P-traps could mitigate styrene emissions in CIPP installations, while the use of a Worker Monitoring System (WMS) may be effective as a tool for health exposure assessment, though further validation is necessary. Indoor air quality research demonstrated that the level of exposure to styrene varied among factors such as ventilation and leakage, hence requiring further investigation into the health hazards of indoor pollution [24]. The concentrations emanating from styrene due to CIPP installations are temporary in nature and decrease quickly to minimize risks outside the immediate safety perimeters; further studies are required to develop models for emissions considering variable environmental conditions [25]. Research has also found that non-styrene polyester resins and styrene emissions from CIPP installations are within safe exposure limits, prompting calls for further exploration of alternative resins and curing methods to improve safety [26].