environmental pollutants

what is environmental pollution?

• environmental pollutants → chemicals that enter the environment as a result of a human activity and pose hazards to health (hazard ≠ risk)

• contaminants/pollutants = chemicals in the environment

• toxicants = toxic synthetic chemicals

• toxins = naturally produced toxic substances

• some pollutants are naturally occuring but harmful due to excess concentration from humans

sources of pollutants

• industrial and agricultural

  • pesticides

  • fertilizers

  • industrial discharge (example: large vietnamese fish kill)

• consumer products

  • pharmaceuticals

  • personal care products

  • plastics

• local vs distant sources

  • local: direct discharges (e.g. untreated undustrial waste → mass fish kill)

  • distant: long range atmospheric trasnport (LRT), where chemicals travel thousands of km and deposit in the arctic

• primary vs secondary emissions

  • primary: direct release (e.g. pesticides applied to fields)

  • secondary: remobilisation of stored pollutants (e.g. POPs re-released by melting ice)

global chemical production and inventories

• chemical production is massive and growing

• >300 million tons/year industrial chemicals

• >100,000 synthetic chemicals in daily use

• combined global chemical inventories = 355,000 subtances

• environemtnal monitoring can only track a tiny fraction of these chemicals, making unknown risks common

WHO “Chemicals of major public health concern”

• hazardous pesticides

• mercury, lead, cadmium

• dioxins

• important becasue these represent substances with global health + environmental relelvance

case study: agent orange / dioxin (TCDD)

what is agent orange?

• a 1:1 mixture of herbicides 2,4-D and 2,4,5_T

• contaminated with TCDD (dioxin), a highly persistent, highly toxic by-product

Chemical properties

• extremely lipophilic

• very low water solubility

• resistant to degredation → therefore hoghly persistent and bioaccumulative

ecological impacts

• 3.1 million hectares of rainforests destroyed

• 40% of mangroves lost

• bird and mammal diversity massively reduced in sprayed regions

human health impacts

• multi-generational effects

• cancers, congenital disabilities, endocrine effects

this case demonstrates key environmental pollutant themes:

• persistence, bioaccumulation, toxicity

• long term legacy contamination

• transgenerational effects

types of environmental pollutants 

• metals and trace elements

  • essential metals (Cu, Se) vs. non essential metals (Hg, Pb, Cd)

  • metal toxicity often arises becasue non-essential metals mimic essential ones, entering uptake pathways

• organometals

  • e.g. tributyltin antifouling paints

• organic pollutants

  • PAHs

  • halogenated organics

  • other organics

• radioactive isotopes

• pahramceuticals and pesticides

• plasticizers, detergents, consumer product additives

criteria for priority substances: P, B, T

• P → persistence

  • long half life, resistant to degredation

• B → bioaccumulation

  • lipophilic compounds accumulate in tissues and biomagnify

• T → toxicity

  • acute or chronic effect; endocrine disruption; carcinogenicity

• some chemicals are vP/vB = very persistent / very bioaccumulative → extreme concern

metals: toxicity and bioaccumulation

• methylmercury fromed in aquatic systems

• biomagnifies through food chains → highest in top predators

• neurotoxic, especially in developing children

• minamata disease as a historical extreme case

organic pollutants

• why they persist?

  • strong C-Cl or C-F bonds

  • resistant to degredation

  • lipophilic → stored in fatty tissue

• POPs (persistant organic pollutants)

  • defined under the stockholm convention

    • persistant

    • bioaccumulative

    • toxic

    • long range transported

• these are found even int eh arctic due to LRT

pollution in the arctic

• a sink for LRT pollutants

• under increasing local pollution pressure from shipping and petroleum activity

• experiencing remobilsation of legacy pollutants as wamring melts ice

• increasing temperatures → synergystic effects between climate stress and pollution

multiple stressors: additive, antagonistic, synergistic

• this concept becomes essential when integrating temperature with contaminant stress

bioaccumulation, bioconcentration, biomagnification

• bioaccumulation - net uptake and retention over time

• bioconcentration → direct uptake form water

• biomagnification → concentration increases up the food chain

• toppredators have the highest burdens

toxicc effects and biomarkers

• immune impacts

• reproductive impairment

• neurotoxicity

• endocrine disruption

• DNA damage

• altered enzyme activity

• bone density changes

• behavioural effects

organic pollutant groups and calssifications schemes

• by functional group

• by properties

• by use

• this is important for ecological risk assessment

petroleum hydrocarbons and oil pollution

• oil = Z95% hydrocarbons

• contains aliphatics, aromatics, PAHs (toxic and carcinogenic)

• oil spills + chronic small releases both matter

• deepwater horizon as an example of complex fate and trasnport

pesticides

• inorganic metals

• organichlorines

• organophosphates

• pyrethroids

• neonicotinoids

• many pesticides are designed to be biologically active - inherently toxic

• affect non-target species

• mixture toxicity common in soils

time trends in arctic pollutants

• many POPs declniing due to regulation

• some pollutant rising due to local source

• climate change complicates trends by altering transport and bioaccumulation

emerging issues: deep sea contamination

pollution is now global and reaches extreme environments

summary: main takeaways for exam

• pollution sources are global, diverse, and increasing

• chemical properties (P, B, T) determine environmental behaviour

• POPs travel long distances and bioaccumulate up foodwebs

• metals, organis, pesticides, hydrocarbon all have distinct mechanisms of toxicity

• arctic ecosystems are highly vulnerable due to long-range trasnport + climate change

• multiple stressors often produce synergistic effect

• pollutants can causes ecological collapse, transgenerational effects, and persistant bioaccumulation

• agent orange illustrates extreme long term impacts of persistant toxic chemicals

papers summary

• pollutants directly reduce biodiveristy

• pollutants interact with other stressors

• adaptation to pollutants is possible but costly

• ecological impacts are multilayered

  • species declines

  • impaired reproduction

  • altered food webs

  • reduced ecosystem resilience

• pollutants have biological activity

• multiple stressors often lead to synergistic effects

• climate change amplifies toxic impacts

• contaminants persist, bioaccumulate, and casues long term ecosystem damage