Lecture 8: Emerging Contaminants
Lecture Notes on Emerging Contaminants
Overview of Emerging Contaminants
Objectives of the lecture:
Understanding emerging contaminants and their impact.
Discussing potential solutions to address them.
Definitions
Contaminant:
Defined as inputs of alien and potentially toxic substances into the environment.
Not all contaminants cause pollution due to low concentrations.
Pollutant:
Specifically refers to anthropogenically introduced, manmade substances that have harmful effects on the environment or human health.
All pollutants are contaminants, but not all contaminants are pollutants.
For example:
Sugar in water = contaminant (not harmful)
Mud in water = pollutant (potential harm)
Diagram of Contaminants
Three categories:
Neutral substances
Contaminants (substances not supposed to be there)
Pollutants (a subset with harmful effects)
Current Trends in Contaminants
New names in the news regarding contaminants:
Agrochemicals affecting water quality.
Presence of antibiotics in water.
Microplastics among emerging contaminants causing public health concerns.
Projected total global antibiotic consumption is a growing concern, with significant increases estimated between 2000 and 2030 across various scenarios.
Cancer Villages: Areas with high cancer rates linked to pollutants from nearby industries.
Emerging Contaminants
Definition:
Contaminants not previously detected and now recognized with different occurrences and potential sources.
Chemicals are being discovered in the environment that previously had not been detected or are being detected at levels that may be significantly different than expected.
Often described as "contaminants of emerging concern" due to risks to health and the environment associated with their presence, frequency of occurrence, or source.
A contaminant also may be "emerging" because of the discovery of a new source or a new pathway to humans.
Examples of Emerging Contaminants
Sources include:
Pharmaceuticals
Pesticides
Industrial chemicals
Surfactants (used in detergents and personal care products)
Personal care products that are consistently being found in groundwater, surface water, municipal wastewater, drinking water, and food sources.
Characteristics of Emerging Contaminants
Lack of Environmental Fate Information:
Environment fate & transport information is lacking.
Example: Microplastics – Transport and life cycle remain poorly understood.
Health Concerns:
Potential health effects on wildlife and humans are not well characterized due to lack of standardized biological testing methods and available data.
Not Routinely Monitored:
Many emerging contaminants exist outside current monitoring lists by regulations (e.g., NEA in Singapore).
Governments often do not have approved methods to detect many of these chemicals.
Potential for Future Regulation:
May require new regulations as understanding improves, depending on their potential human health effects and toxicity.
Consequence of Discovery / Need for New Tools:
Discovery of new sources/pathways can categorize substances as emerging.
New tools are needed to help address the issue.
Sources of Contaminants
Sources classified as:
Point sources: Specific location (e.g., discharge pipes from factories, single sewer, or factory wastewater outfall).
Non-point sources: Diffuse origins that cannot be attributed to any single spot and are thus harder to control (e.g., fertilizers on farmland, runoff of toxic substances after a rain).
Examples of specific contaminant sources:
Pharmaceuticals and Personal Care Products (PPCPs):
Products used by individuals for personal health or cosmetic reasons or by agribusiness to enhance growth or health of livestock.
Comprise thousands of chemical substances, including prescription and over-the-counter therapeutic drugs, veterinary drugs, fragrances, and cosmetics.
Pharmaceuticals: antibiotics, hormones, statins, anti-cancer drugs, veterinary drugs, etc.
Personal Care: sunscreens, colognes, antibacterial soap, detergent, hair spray, etc.
Each person consumes an average of grams of pharmaceuticals per year, with global human drug consumption estimated at tons per year.
Ecotoxicological and human toxicological concerns: PPCPs show considerable persistency and bioaccumulation potential. Some endocrine disrupting compounds (e.g., the hormones) show feminisation or masculinisation effects on aquatic organisms even at low levels.
Pathways of PPCP Contamination:
Humans consume drugs (caffeine, nicotine, pharmaceuticals), metabolizing some but excreting the rest through urine and fecal matter.
These excreted chemicals flow with sewage out of homes.
Most sewage treatment plants filter and chlorinate sewage to remove microbes and organic matter, but typically do not remove pharmaceuticals.
Drug-tainted water can pass through sewage treatment plants into streams and lakes, where it can be taken up by wildlife and drinking water supplies.
This raises concerns about harm to ecosystems and unforeseen consequences due to current safeguards failing to remove these chemicals.
Little is known about the health effects or levels of these pollutants in waters, leading to a lack of solid data for federal and state governments to regulate their release.
Disinfection By-products: Substances formed during disinfection processes in wastewater treatment.
Environmental Impact of Contaminants
Persistency:
Description of persistent organic pollutants (POPs) that resist degradation and bioaccumulate across ecosystems.
Bioaccumulation vs. Biomagnification:
Bioaccumulation: Refers to the increasing concentration of substances in the same organism over time.
Biomagnification: Refers to increasing concentrations of substances in organisms at each level of the food chain (e.g., DDT).
Endocrine Disrupting Chemicals (EDCs)
Definition:
Substances in the environment (in the air, soil, or water supply), food sources, and manufactured products that may interfere with the normal functioning of our body's endocrine system.
The endocrine system is made up of glands that produce and release chemical messengers called hormones.
When absorbed in the body, an endocrine disruptor can decrease or increase normal hormone levels, mimic the body's natural hormones, or alter the natural production of hormones.
Health Implications:
EDCs can lead to cancer, reproductive issues, developmental, and neurological disorders. Examples include:
PFA (Per- and Poly-fluorinated alkyl substances)
Bisphenol A (BPA)
Dioxins
Example Case Studies
Triclosan:
A substance once hailed for its antibacterial properties, now considered hazardous due to potential hormone disruption and antimicrobial resistance.
Common products containing Triclosan include liquid soaps (e.g., Dial® Liquid Soap), deodorants (e.g., Right Guard Sport), dental care products (e.g., Colgate Total® Toothpaste), and some kitchenware and children's toys.
In 2017, FDA required pre-market approval for use.
The FDA at the time of review reported that Triclosan was not known to be hazardous to humans but had insufficient safety evidence to recommend changing consumer use. They also found no evidence that Triclosan in antibacterial soaps offered extra health benefits over regular soap and water, advising concerned consumers to use regular soap and check product labels.
PFOA (Perfluorooctanoic Acid):
Found in Teflon products; linked to chronic illnesses and found in blood of many individuals.
Persisting in the environment indefinitely, it remains in people for a very long time.
PFOA causes developmental and other adverse effects in laboratory animals.
Nanomaterials
Definition: Materials with at least one dimension smaller than nanometers.
Characteristics and uses in:
Electronics
Personal care products (e.g., sunscreens)
Concerns regarding ecotoxicity and potential health effects due to their small size.
Solutions and Advancements
Current Efforts:
Agencies like the US EPA and WHO are working to manage and regulate emerging contaminants.
Emerging contaminant life cycle includes:
Awareness and characterization.
Analytical techniques (e.g., GCMS, HPLC).
Management and remediation strategies.
Regulation.
Strategies for controlling ECs encompass various measures, including pollution control at the source, sustainable remediation to clean up contaminated sites, and sustainable management practices to prevent contamination.
Need for Policy:
Science-informed policies essential for addressing the risks and establishing regulations.
Key Takeaways
Emerging contaminants pose significant health and environmental risks, highlighting a need for increased awareness, monitoring, and regulation.
Characteristics including persistency and bioaccumulation underline the importance of lifestyles that reduce the introduction of these contaminants into the environment.
These pollutants enter lakes and rivers, harming fish and aquatic life, and can bioaccumulate in the food chain, affecting non-aquatic species that consume contaminated fish.
Research shows they can disrupt endocrine systems, causing health issues in humans and wildlife.
Regulatory bodies like the USEPA are working to control and ban these harmful substances.
Future studies and advancements in technology, along with cooperation from international bodies, are critical for addressing these emerging issues effectively.