Emerging Air Pollutants: Risks, Sources, and Environmental Impact

Air pollution has long been associated with well-known pollutants like carbon monoxide, sulfur dioxide, and particulate matter. However, a new category of contaminants, known as emerging pollutants, is silently infiltrating our atmosphere. These pollutants, often overlooked by conventional air quality monitoring systems, originate from industrial chemicals, pharmaceuticals, microplastics, and even antimicrobial-resistant bioaerosols. While their presence may be in trace amounts, their long-term impact on human health and the environment is alarming.

At a recent event by the Indian Air Quality Network (IAQN), Dr. Nirmal Kumar J. I. highlighted how these pollutants are found across environmental components, air, water, soil, and even living organisms. The challenge? Limited regulations, lack of comprehensive monitoring, and unclear long-term consequences. Unlike traditional air pollutants, these emerging contaminants are not fully addressed by current policies, making their mitigation complex.

This blog explores the rise of emerging air contaminants, their impact on health and ecosystems, and why policymakers, researchers, and industries must act now. With growing urbanization and industrialization, understanding these pollutants is no longer optional. It is essential for a healthier and more sustainable future.

What Are Emerging Air Pollutants?

Emerging pollutants, also known as contaminants of emerging concern (CECs), are chemicals that frequently escape detection due to a lack of regular monitoring, but they possess the potential to penetrate the environment. These substances are present in minute quantities and encompass a vast array of both organic and inorganic compounds, including pharmaceuticals, pesticides, microplastics, and heavy metals, quietly influencing the environment that we inhabit.

A variety of emerging pollutants tend to remain in the environment for extended durations, leading to their accumulation in water, soil, and living organisms over time. The ongoing presence of these substances results in bioaccumulation within the food chain, which may lead to lasting health hazards for both humans including potential endocrine disruption, cancer-related effects, and reproductive challenges.

These substances enter the atmosphere through processes such as volatilization, aerosol production, and diffusive exchange. They are subsequently transported to nearby or distant areas via dry and wet deposition or wind events. A research study in 2021 revealed the detection of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers in isolated high-altitude European lakes. This finding highlights the long-range atmospheric transport of these pollutants from urban areas to remote locations through aerosol particles. Factors like temperature, precipitation, wind speed, and boundary-layer mixing play a crucial role in shaping the movement patterns of airborne pollutants. The various layers of the atmosphere, primarily consisting of outdoor and ambient air, along with atmospheric deposition and dust from roadways, have become significant transporters of airborne pollutants and sources of emerging contaminants affecting both land and water ecosystems.

Therefore, comprehending the routes and processes by which Emerging contaminants move is essential for evaluating their effects on the environment. The movement of these pollutants across diverse ecosystems leads to interactions with various environmental matrices, resulting in changes to their chemical composition and potential toxicity. Consequently, pinpointing the main sources and particular instances of these pollutants is crucial for formulating effective reduction strategies and safeguarding environmental health.

Selected Emerging Pollutants

• Microplastics and Nano Plastics: Microplastics are defined as plastic fragments measuring less than 0.5mm in diameter, comparable in size to a grain of rice. In contrast, nanoplastics measure a mere 100 nanometres or even smaller.

• Synthetic Organic Chemicals: Organic pollutants are harmful molecules emitted from various industrial products, including detergents, petroleum hydrocarbons, plastics, organic solvents, pesticides, and dyes. Additionally, volatile organic compounds (VOCs) such as acrylonitrile, 1,3-butadiene, chloroform, and formaldehyde also contribute to this issue.

• Antimicrobial Resistance: The issue of antimicrobial resistance is becoming increasingly significant, particularly as it can be transmitted via bioaerosols in various environments, both indoors and outdoors. This phenomenon raises concerns about the potential rise in antibiotic resistance among human and animal populations.

• Heavy Metals: Specific metals like arsenic, manganese, and vanadium are recognized as emerging pollutants because they are found in the atmosphere due to industrial emissions and pose potential health risks.

• Engineered Nanoparticles: encompass materials such as metal oxides and quantum dots, utilized across a range of applications. Their small size and reactivity can lead to airborne dispersion, raising potential risks.

• Bioaerosols: They consist of biological particles present in the atmosphere, such as bacteria, viruses, and fungi. These particles have the potential to transport emerging pollutants and pose various health risks.
  

Sources of Emerging Pollutants

Emerging pollutants originate from various natural and anthropogenic sources, encompassing a wide range of chemical and biological materials. Understanding these sources is crucial for developing effective management and mitigation strategies.

Emerging Pollutants in the air are mostly caused by anthropogenic activities, but natural sources also play a big role.

Natural Origins of Emerging Air Contaminants

• Volcanic Eruptions: Volcanic eruptions emit a range of metals and various elements into the air.

• Forest Fire: It releases polycyclic aromatic hydrocarbons (PAHs) along with various organic compounds.

• Biogenic Emission:  Natural processes, including those from plants, can emit volatile organic compounds (VOCs) that play a role in the creation of secondary organic aerosols, which are a type of emerging pollutant.
  

Human-Caused Origins of Emerging Air Contaminants

• Industrial Processes: The manufacturing and application of industrial chemicals, such as nanoparticles and rare earth elements, release Emerging pollutants into the air.

• Agricultural Activity: The application of pesticides and fertilizers in agricultural practices can result in the emission of endocrine-disrupting compounds and various pollutants into the atmosphere.

• Pharmaceuticals and Personal Care Products (PPCPs): These substances that can significantly impact environmental health. Their presence in various ecosystems raises concerns about potential effects on both human and ecological systems. The presence of these substances in wastewater can lead to their volatilization and subsequent release into the atmosphere, thereby adding to the array of emerging air pollutants.

• Urbanization and Industrialization: The swift expansion of urban areas and industrial operations in developing regions contributes notably to the rise of Emerging pollutants, such as heavy metals and synthetic organic compounds.
  

Airborne Microplastics and Health Risks

Airborne microplastics (MPs) are tiny plastic particles, often smaller than 10 microns, that can be inhaled and settle deep in the lungs. Because of their small size, they bypass the body’s natural defenses and reach the alveoli, where oxygen exchange happens. Studies show that prolonged exposure can cause lung inflammation, oxidative stress, and tissue damage, potentially leading to respiratory diseases like asthma, COPD, and lung fibrosis.

Microplastics also carry chemical additives and toxins that may interfere with hormones and increase health risks. Did you know this? A 2023 study found that inhaled microplastics can reach deep into the lungs, settling in the alveoli, where oxygen exchange happens. This buildup may cause inflammation and affect lung function, raising concerns about respiratory health.

Since research on the health effects is still developing, stronger regulations and better air quality monitoring are needed. Reducing industrial emissions, improving filtration systems, and controlling plastic waste in the environment can help lower exposure and protect public health.

Monitoring of Emerging Contaminants

The detection and quantification of emerging contaminants require advanced analytical techniques, efficient sampling strategies, and optimized extraction procedures. Each method has its strengths and limitations, influencing its suitability based on factors such as pollutant characteristics, sensitivity requirements, and available resources.

Sampling Methodologies

Emerging contaminants can be sampled through active sampling, passive sampling, and biomonitoring, each offering distinct advantages and trade-offs.

• Active Sampling utilizes pumps to draw air through filters or sorbent materials, enhancing sample quantity and precision. While this method ensures high sensitivity and control over sampling volumes, it is expensive, requires a power source, and demands regular maintenance.

• Passive Sampling relies on natural diffusion or adsorption onto sorbents over time, making it more cost-effective and energy-efficient. However, its sensitivity is lower compared to active sampling, and extended exposure durations may be necessary to accumulate sufficient analytes.

• Biomonitoring leverages living organisms, such as tree leaves, to capture airborne pollutants. This technique provides spatial and temporal insights into contamination patterns while being non-invasive. Nonetheless, results can vary significantly due to species-specific differences, and indirect measurement techniques limit its precision.

Extraction Techniques

Efficient extraction of contaminants from collected samples is crucial for accurate detection. Several techniques offer different benefits in terms of efficiency, solvent usage, and processing time:

• Solid-liquid extraction (SLE) is a simple and cost-effective method where contaminants are dissolved using solvents. Despite its ease of use, it requires substantial solvent volumes and can be time-intensive.

• Soxhlet Extraction continuously circulates solvents to extract persistent organic contaminants efficiently. However, the process is both time-consuming and solvent-intensive, making it less favourable for high-throughput analysis.

• Ultrasound-assisted extraction (UAE) employs ultrasonic waves to enhance extraction efficiency while minimizing solvent consumption and reducing processing time. Its primary limitation is the potential degradation of thermolabile compounds due to ultrasonic energy.

• Pressurized Liquid Extraction (PLE) applies high pressure and temperature to improve extraction efficiency while using fewer solvents. Although it enhances analyte recovery, the requirement for specialized and costly equipment can be a drawback.

• Supercritical Fluid Extraction (SFE) uses CO2 as a solvent, offering an environmentally friendly and highly selective approach. However, the technique demands specialized instrumentation and precise operational control.

• Thermal Desorption (TD) volatilizes contaminants for direct analysis, eliminating solvent use and enabling automation. This method is well-suited for volatile and semi-volatile compounds but is ineffective for non-volatile substances.

Analytical Techniques

Once extracted, contaminants are analyzed using various sophisticated techniques, each offering unique capabilities:

• Gas Chromatography-Mass Spectrometry (GC-MS) is highly sensitive and well-suited for volatile and semi-volatile compounds. However, polar molecules often require derivatization before analysis, adding complexity.

• Liquid Chromatography-Mass Spectrometry (LC-MS) is ideal for detecting non-volatile and polar contaminants with high accuracy. While effective, it requires intricate sample preparation and is more expensive than GC-MS.

• Fourier Transform Infrared Spectroscopy (FTIR) enables rapid, non-destructive analysis but has limited sensitivity and selectivity compared to other methods.

• Capillary Electrophoresis-Mass Spectrometry (CE-MS) provides high-resolution separation with minimal solvent usage, though its applicability is somewhat restricted due to technical constraints.

• Nuclear Magnetic Resonance (NMR) offers comprehensive structural information about contaminants but requires large sample volumes and costly instrumentation.

Challenges in Monitoring

Monitoring organic pollutants in the air is complex due to their diverse chemical properties and varying environmental behaviours. Detecting and analyzing these substances present multiple challenges, categorized into technical, methodological, and logistical difficulties. Below are the primary obstacles in monitoring organic contaminants in the atmosphere.

1. Calibration and Precision: Ensuring the accuracy of monitoring systems requires proper calibration using reference gas mixtures traceable to international standards. This guarantees data consistency and comparability across different monitoring networks.

2. Measurement Errors: Many existing monitoring devices have significant error margins and require frequent recalibration. Advanced monitoring technologies now incorporate error correction algorithms and statistical calibration analysis to improve accuracy.

3. Gas-Particle Dynamics: Organic pollutants can exist in both gaseous and particulate forms, making their measurement more challenging. Their phase distribution affects their transport, deposition, and health impact, necessitating advanced analytical techniques for precise assessment.

4. Global Monitoring Constraints: Large-scale monitoring efforts face difficulties in establishing representative sampling sites and ensuring uniform data collection across different geographical regions. Initiatives like the Global Monitoring Plan under the Stockholm Convention attempt to address these issues, but regional pollutant concentration differences remain a major hurdle.

5. Resource Availability: In many developing nations, monitoring efforts are constrained by high equipment costs and a lack of specialized personnel. This leads to limited monitoring frequency and a focus on pollutants that are easier to detect.

Towards a Smarter and Sustainable Future

The rapid emergence of airborne contaminants—ranging from microplastics and toxic chemicals to antimicrobial-resistant bioaerosols and heavy metals—poses a significant threat to environmental and human health. Unlike traditional pollutants, these substances persist undetected, accumulating in ecosystems and human bodies while bypassing outdated regulatory frameworks. The lack of comprehensive monitoring and effective policies further exacerbates the issue, leaving populations exposed to long-term consequences that remain poorly understood.

However, technological advancements present promising solutions. Artificial intelligence (AI) and big data analytics are revolutionizing environmental monitoring, enabling predictive pollution models and real-time data analysis. The integration of Internet of Things (IoT) technology enhances automation, broadens coverage, and improves the accuracy of monitoring networks. Nevertheless, widespread adoption depends on cost reduction and the establishment of standardized protocols to ensure seamless system integration.

Collaboration among policymakers, researchers, and industry leaders is essential to overcoming financial and technical barriers in pollutant monitoring. Strengthening regulatory frameworks, investing in cutting-edge monitoring technologies, and adopting sustainable practices will be crucial in mitigating the risks associated with emerging contaminants. The urgency of addressing air pollution cannot be overstated—immediate action is necessary to safeguard both the environment and public health. The steps taken today will determine the air quality and overall well-being of future generations.