Catharanthus roseus L. and Ocimum sanctum L. as Sensors for Air Pollution

Introduction

The expansion of urban areas, the acceleration of traffic, the acceleration of economic growth, and the excessive use of energy are all characteristics of industrialized nations that have contributed to the worsening of air pollution. The integrity of the natural world is compromised by all these elements, which have a domino effect on one another and work together to harm it. A study conducted by Kumar and Bhattacharya (1999) compared the rates of economic growth, industrial pollution, and vehicular pollution in India from 1975 to 1995. The results showed that when the Indian economy grew 2.5 times, industrial pollution increased by 3.5 times, and vehicular pollution by 7.5 times. Due to the emigration of rural Indians seeking employment opportunities in urban centers, most Indian cities are seeing faster-than-average population growth. Cities are growing and merging with one another because of this. The issue of air pollution has arisen as a result of significant population influxes to metropolitan regions, rising consumption habits, and uncontrolled industrial and urban expansion. Point sources, mobile sources, and interior sources are the three main categories of human-caused air pollution. The use of open fires for cooking and heating may cause significant indoor air pollution in developing nations, particularly in rural regions. Distant sources of air pollution include factories, power plants, and other industrial facilities. However, in both wealthy and developing nations, mobile sources, especially pollution from cars, are the main culprits when it comes to poor air quality in metropolitan areas. Automobile use is expanding rapidly over the world, especially in developing nations (Yunus et al., 1996). India has also seen a surge in car sales in recent years. In India, air pollution is a serious problem in cities, where vehicles constitute a big part of the problem, and in other places where thermal power plants and industrial facilities are concentrated. Increasing levels of air pollution in metropolitan areas throughout the globe have been linked to motor vehicles (Mage et al., 1996; Mayer, 1999). When compared to other cities across the globe, the pollution level in Indian cities is increasing owing to the emissions from cars running all the time, according to the National Environmental Engineering Research Institute (NEERI). Sixty to seventy percent of the pollution in metropolitan areas is caused by vehicles, which considerably adds to the air pollution load (Singh et al., 1995). In India's major cities, air pollution from cars is a major and quickly expanding issue (UNEP/WHO, 1992; CSE, 1996), as it is in many other regions of the world. A number of India's largest cities have severe air pollution problems, with vehicle exhausts being named as a key source of this issue (CPCB, 1999, 2000). The problem has been made worse by the high concentration of automobiles and the relatively high ratio of motor vehicles to inhabitants in these cities (CRRI, 1998; CSE, 2001). Concerns about energy security and global warming are heightened by the fast increase in the use of motor vehicles. Nearly half of the world's oil is currently used by transportation. In the ten years after the 1990s, transportation related energy consumption and carbon dioxide emissions increased by almost one third; low income nations accounted for over half of this growth (Grubler, 1994). The use of petroleum products in India has almost quadrupled in the last ten years, with transportation accounting for half of this increase. The road industry alone consumes 25% of India's total energy, with 98% of it coming from oil. Diesel usage is six times higher than gasoline consumption, despite the fact that gasoline cars constitute the vast majority of vehicles (around 85%). Also contributing to the dramatic rise in fuel usage is the steady transition of freight and passengers away from rail and onto roads (CRRI, 1998). Approximately one million tons of pollutants are discharged into the atmosphere daily in all of the country's major cities, with 75% of that amount coming from vehicles (Chauhan et al., 2004). Hydrocarbons (including aldehydes, single and poly aromatic hydrocarbons, alcohols, olefins, alkylnitrites), carbon particles, heavy metals, water vapour, and oxides of sulfur (SO₂), carbon (CO₂), and nitrogen (NO₂) are the primary pollutants from exhaust, while a variety of secondary pollutants, including ozone, contribute to harmful environmental and health effects (Pandey et al., 1999; Kammerbauer and Dick, 2000). Incomplete combustion of fossil fuels produces polycyclic aromatic hydrocarbons (PAHs), a type of ubiquitous organic chemicals in the environment. Some of these PAHs are very concerning due to their mutagenic and carcinogenic properties (IARC, 1983). It is believed that car exhausts are the primary source of these persistent organic pollutants in large metropolitan conurbations. It is estimated that in the main metros of India, automobiles are responsible for 70% of CO, 50% of HC, 30-40% of NO₂, 30% of SPM, and 10% of SO₂ pollution. Out of this total, two-wheelers contribute two thirds. Respiratory and other air pollution related illnesses, such as lung cancer, asthma, etc., are mostly caused by these elevated amounts of contaminants (CPCB, 2002; Sengupta et al., 2001).