PHAR303 Lecture 20 Environmental and Occupational

chemicals detected in south African children

• Project

  • Monitors environmental chemical exposure in remote communities in South Africa

• Silicone wristbands

  • Worn by 5–6-year-old children

  • Worn for 72 hours

  • Wristbands collect environmental chemical exposures

• Chemicals detected

  • Many chemicals identified, including known toxicants:

    • Plasticizers

    • DDT (insecticide)

    • Organophosphate esters (flame retardants)

    • PAHs (polycyclic aromatic hydrocarbons)

• Source of PAHs

  • Mainly from family cooking over open fires

movement of chemicals in environment - exposome

• Exposome

  • Measures all chemical exposures an individual experiences

  • Analyzes the overall impact of environmental chemicals on the body

• Previous approach

  • Analyzed each chemical separately

• Current approach

  • Can analyze many chemicals simultaneously

  • Uses samples such as a drop of blood

• Chemical analysis

  • Depends on the physical and chemical properties of chemicals

  • Uses these properties to predict where a chemical will be found in the body/environment

ecozones in canada

• Cyclical movement of toxins

  • Toxins can move through the environment and food chains

  • Exposure can occur independently of human control

• Agricultural and urban-based regions

  • Issues include:

    • Drinking water quality

    • Urban congestion

    • Air pollution

    • Wildlife loss

• Coastal regions

  • Problems include:

    • Declining fish stocks

    • Land-based pollution

    • Forestry impacts

• Arctic regions

  • Reduced contamination of traditional foods

  • Environmental concerns linked to climate change impacts

environmental chemodynamics

• Chemical movement in the environment

  • Chemicals move between different environmental compartments

  • Their physical and chemical properties determine their behavior and movement

• Chemical partitioning

  • Properties of a chemical allow prediction of how it will distribute between:

    • Air

    • Water

    • Soil

    • Biological systems (living organisms)

what constitutes an environmental toxicant

persistence

bioaccumulation and biomagnification

toxicity

persistence

• Half-life (T1/2) of toxic chemicals

  • Huge differences exist between half-lives of toxic chemicals

  • Atrazine: ~25 months

  • DDT: ~10 years

• Chemical removal

  • Takes approximately 4 half-lives for a compound to be removed from the environment

• Sources of these chemicals

  • Often used as:

    • Insecticides

    • Herbicides

    • Pesticides

  • Can also result from tobacco products

• Sustained exposure

  • If the exposure rate is sustained, the half-life becomes irrelevant

  • Toxicants are continuously entering the system

bio accumulation and magnification

• Bioaccumulation

  • Accumulation of contaminants from food and the environment

  • Positively correlated with lipophilicity

• PCB example

  • Large cleanup attempts have occurred

  • Still found in the Great Lakes

  • Difficult to remove

• Biomagnification

  • Due to food digestion and absorption

  • Contaminants can become concentrated in the GI tract

  • Levels increase in organisms as you move up trophic levels

  • Humans are at the top of the food chain, making us susceptible

• DDE example

  • DDE is a metabolite of DDT

  • Low levels found in water

  • As it moves up the food chain, concentrations increase

  • Birds at higher trophic levels have much higher amounts of DDE

toxicity

• Persistence, bioaccumulation, and biomagnification

  • Do not matter if the substance is not toxic

• Ways of testing toxicity

  • Structure–activity relationships

  • In vitro tests

  • Short-term tests

  • Animal bioassays → being phased out

  • Epidemiological data

    • Long-term

    • Hard to rely on

Stockholm convention of persistent organic pollutants

• Chemicals in the environment

  • Can come from many different sources

  • Many countries, including Canada, participate in international agreements

• Stockholm Convention

  • Established in 2004

  • Focuses on persistent organic pollutants (POPs)

  • Considers:

    • Toxicity

    • Persistence

    • Bioaccumulation

    • Biomagnification

• Goal

  • Eliminate or significantly reduce the release of POPs into the environment

• Examples of POPs

  • Pesticides

  • Industrial chemicals

  • PCBs

  • DDEs

POPs in polar bears Canadian arctic

• Chemical accumulation in polar bears

  • Many chemicals are found in bear adipose tissue

• PCBs and DDE

  • Among the first chemicals identified

  • Included in the 12 POPs under the convention

• Polar bears

  • Still contain high levels of PCBs and DDEs

PCBs in mothers and babies in Nunavik

• PCBs and neurodevelopment

  • PCBs may be related to anxiety symptoms in Inuit preschoolers

  • PCBs have effects on child neurodevelopment

• Effects of PCBs

  • Effects can differ depending on the endpoint being measured

applications of the Stockholm convention

• Stockholm Convention

  • 12 initial chemicals were outlined

• Approaches for controlling chemicals

  • Annex A: Elimination

    • Complete ban of chemicals

  • Annex B: Restriction

    • Used when a chemical is considered absolutely essential

    • Example:

      • DDT was not globally eliminated

      • Restricted because it prevents malaria in Africa

      • Canada eliminated DDT because:

        • No malaria risk

        • Alternative options are available

  • Annex C: Unintentional production

    • Attempts to prevent unintentional production of chemicals

• Updates to the convention

  • 16 additional chemicals added in 2009

  • Some were:

    • Eliminated

    • Restricted

    • Difficult to find substitutes for

  • Meetings occur every year

  • Now approximately 30 chemicals are listed

  • Canada ratified the list of 21 chemicals

tetrabromodiphenyl ether and PFOA and PFOS

• Tetrabromodiphenyl ether

  • Used as a flame retardant

  • Not approved for use in Canada

  • Gradually being replaced with alternative chemicals

  • Some alternatives may also have negative effects

• PFAS chemicals

  • Examples:

    • PFOA

    • PFOS

  • Efforts are being made to replace them

  • Alternatives include short-chain compounds

  • Short-chain alternatives are also showing potential toxicity

• Regulation

  • Environment and health ministers stated they would:

    • Assess and regulate the entire chemical family

    • Not only individual compounds

PFOS and PFOA

PFAS

• Includes industrial surfactants and dispersants

• Used in:

  • Non-stick pans

  • Waterproofing

  • Firefighting foam

• Exposure

  • Firefighters have the highest exposure

  • Exposure routes:

    • Oral intake (fish, drinking water)

    • Inhalation

• Persistence

  • Human half-life: ~2.7 years

  • Quite persistent

  • Longer-chain PFAS → longer half-life

  • Groundwater persistence: 5–15 years

• Sources

  • Produced as industrial by-products

  • Found in:

    • Airports

    • Military sites

    • Canada

• PFAS in the Arctic

  • PFOA and PFOS found in surface water

  • Chemicals are dispersed throughout the Arctic

  • Chemicals produced in urban areas travel north through:

    • Wind

    • Water currents

  • Represents a global issue

• High levels of PFOS and PBDEs found in polar bears

PFOA toxicity

• Tetrabromo ether

  • Used as a flame retardant

  • Not approved for use in Canada

  • Gradually being replaced with alternative chemicals

  • Some alternatives may also have negative effects

• PFAS chemicals

  • Examples:

    • PFOA

    • PFOS

  • Efforts are being made to replace them

  • Alternatives include short-chain compounds

  • Short-chain alternatives are also showing potential toxicity

• Regulation

  • Environment and health ministers stated they would:

    • Assess and regulate the entire chemical family

    • Not only individual compounds

sses indsutrial surfacnats and diosperants like nonstick pan waterrooignf fir efighting foam firefighters have highest exposure expsore oral fish drinkinf water inhaltion half life humans 2.7 years quite persisnt llonger chain longer half life groundwater 5-15 years produced as indsutrial byprodcyst pfas in canada airports militaru pfoa and pfos in surface water artic chemicals are dispered all over arctoc chems produced in urban travel north from wind and water currents global issue only in surface water not in animals where theres bio and biomagnification high levels of pfos and pbdes in north polar bears

• PFAS

  • Includes industrial surfactants and dispersants

  • Used in:

    • Non-stick pans

    • Waterproofing

    • Firefighting foam

• Exposure

  • Firefighters have the highest exposure

  • Exposure routes:

    • Oral intake (fish, drinking water)

    • Inhalation

• Persistence

  • Human half-life: ~2.7 years

  • Quite persistent

  • Longer-chain PFAS → longer half-life

  • Groundwater persistence: 5–15 years

• Sources

  • Produced as industrial by-products

  • Found in:

    • Airports

    • Military sites

    • Canada

• PFAS in the Arctic

  • PFOA and PFOS found in surface water

  • Chemicals are dispersed throughout the Arctic

  • Chemicals produced in urban areas travel north through:

    • Wind

    • Water currents

  • Represents a global issue

• Bioaccumulation and biomagnification

  • PFAS detected in surface water

  • Not only in water — also found in animals where bioaccumulation and biomagnification occur

  • High levels of PFOS and PBDEs found in polar bears

animal studies: reproducitve, developmental, liver, kidney, immunological, canver, ( epidemological: incrwased cholesterol low infant birth weight immunolical canver thyroid hormone and endo crine disurutopn

• Animal studies

  • Effects studied include:

    • Reproductive effects

    • Developmental effects

    • Liver effects

    • Kidney effects

    • Immunological effects

    • Cancer effects

• Epidemiological studies

  • Associated with:

    • Increased cholesterol

    • Low infant birth weight

    • Immunological effects

    • Cancer

    • Thyroid hormone changes

    • Endocrine disruption

DuPont case

PFAS lawsuits

• Personal injury lawsuits filed against DuPont

• Related to contamination of drinking water in Ohio and Virginia

• Involved exposure to PFAS chemicals

• Settlement

  • Agreement reached after decades of exposure

  • Approximately $4 billion used to settle lawsuits involving PFAS use

• “Forever chemicals”

  • PFAS are called forever chemicals

  • Difficult to remove from the environment

• Regulation

  • Some PFOS and PFOA regulations are state-specific in the USA

occupational toxicology

Occupational toxicology

• Application of toxicology principles and methods

• Focuses on biological and chemical hazards in the workplace

• Objective

  • Prevent adverse health effects in workers

• Workers at risk

  • Miners

  • Farmers

  • Chemical plant workers

  • Firefighters

challenges in occupational toxicology

• Workplace regulation challenges

  • Difficult to determine the middle ground between:

    • Industry regulations

    • Worker safety

• Regulations

  • Must be put in place to protect workers

  • However, strict regulations can be:

    • Hard to enforce

    • Expensive

    • May drive away investors

    • May cause job losses

• Linking illness to workplace exposure

  • Difficult to establish a clear link between illness and job exposure

  • Example:

    • Miner

    • Family history of cardiovascular disease

    • Difficult to determine if disease came from the workplace or other factors

continued

• Latent interval

  • Time between exposure and disease expression

  • If exposure occurred 20 years ago, it is difficult to prove the disease is related to that exposure

• Asbestos example

  • Easier to link exposure to disease because:

    • Physical asbestos fibres can be found in people’s lungs

• Multifactorial nature of occupational diseases

  • Many diseases have multiple contributing factors

  • Occupational exposure may not be the only cause

exposure to disease prevention

• Occupational exposure assessment

  • Determine what people are being exposed to

  • Consider:

    • Duration

    • Concentration

    • Frequency

• Occupational standards

  • Can help decrease exposure

• Protection methods

  • Use protective equipment

• Surveillance

  • Can identify adverse health effects

  • Monitor workers to help protect them

  • Can perform biomonitoring with worker cooperation

biomonitoring of occupational exposure to BPA BPS and BPF