The population growth of major cities in Iran and the lack of attention to scientific and managerial principles in urban planning in recent years have created numerous issues for citizens and urban planners, pushing cities towards instability. Tehran, as the capital of Iran, is among the cities facing numerous urban challenges. It appears that these factors will present serious challenges to the city's future sustainability. Many articles have assessed and analyzed indicators of sustainability in cities, but less attention has been paid to indicators of instability and real issues that pose challenges to urban planning sustainability. In this regard, the present study aims to identify the challenges of sustainability in urban planning by re-evaluating indicators related to urban sustainability and assessing indicators of instability in urban planning from a realistic perspective. The results indicate that the major indicators of urban planning instability have been summarized into three economic, social, and environmental indices. In the economic index, the unstable components in urban planning include uncertainty in economic policies, housing prices, non-standard housing, income, employment, unemployment, cost of living, and female-headed households. In the environmental index, the unstable components in urban planning consist of climate change, heat islands, floods, transportation management, energy security, noise and air pollution, urban traffic, water quality and quantity, waste disposal quality, urban green infrastructure, environment as an aesthetic issue, and changing the approach to the environment with changes in individuals. In the social index, the unstable components in urban planning encompass social interaction, access to facilities and services, access to social harms services, sense of identity and belonging, neighborly relations, social segregation, public participation in city affairs, and security and welfare.

Aging underground pipeline infrastructure across the United States, including systems used for potable water supply, wastewater collection, and stormwater conveyance, has exceeded its intended service life, emphasizing the need for replacement or rehabilitation to maintain reliable service to communities. Among available trenchless technologies, cured-in-place pipe (CIPP) is widely applied because it minimizes surface disruption and is well-suited for use in densely populated areas. Despite these advantages, environmental concerns remain regarding the release of total volatile organic compounds (VOCs) during CIPP installation and curing. This study evaluates total VOC emissions from CIPP liners under field conditions. Air samples were collected at six installation sites across the United States before, during, and after installation and curing to quantify key VOC species. Multiple sampling methods were employed, including photoionization detectors (PIDs), Summa canisters, and personal worker sampling. The measured compounds included styrene, cumene, acetophenone, hexane, toluene, and ethanol. Measured concentrations were compared with occupational exposure limits established by the U.S. Environmental Protection Agency (USEPA), the National Institute for Occupational Safety and Health (NIOSH), and the Occupational Safety and Health Administration (OSHA). The results indicate that styrene was the dominant compound within active CIPP work zones, with peak concentrations reaching 25.5 ppm during curing. In contrast, VOC concentrations decreased substantially within five feet downwind of the work zone. Overall, the findings suggest that potential public exposure risks are limited, while workers directly involved in CIPP operations may experience elevated short-term exposures during installation and curing activities.

Aging underground pipeline infrastructure across the USA has outlived its design lifespan, highlighting the need to replace or rehabilitate it to ensure continued service to communities. Among trenchless methods, Cured-in-place pipe (CIPP) was chosen to re-pair the damaged pipe since it minimizes surface disruption and is ideal for use in densely populated areas. However, environmental concerns have been raised regarding the chemical compounds involved in the CIPP process. The study focuses on evaluating volatile organic compounds (VOCs) that could be emitted from CIPP liners during the in-stallation and curing process. The results were compared with exposure limits of USEPA, NIOSH, and OSHA to assess potential occupational and worker health impacts. The data were collected from six different sites across the USA and documented VOCs before, dur-ing, and after the installation and curing process. Various devices were used to capture air emissions, including PIDs, Summa canisters, and worker samples. The findings indicated that high styrene concentrations were present within the CIPP work zone. The results also confirmed a considerable reduction in VOC concentrations within five feet down-wind of the work zone. In summary, the results suggest that public health risks appear to be low. However, there are possible health implications for personnel directly engaged in CIPP activities.