Lecture 2 Flashcards
(60 cards)
what are environmental contaminants?
substances that, when accidentally or deliberately introduced into the environment, may have the potential to harm people, wildlife and plants
what are PCDDs (dioxins) and PCDFs (furans)?
- produced unintentionally as by-products of industrial processes such as the combustion of waste products, the manufacturing of pesticides, and other chlorinated substances
- in BC, pulp and paper mills historically intentionally released large amounts into the marine environment
- regulated in 1989 = 95% reduction in the release of these compounds in coastal BC
what are polychlorinated biphenyls (PCBs)?
- industrial chemicals that were used extensively as stable, heat-resistant oils in electrical transformers, and as additives in paint and plastics
- still in the environment, not fully banned until 2025
what is DDT?
- used as an insecticide 1939 onwards
- promoted as an agricultural and household pesticide
- malaria/typhus control agent
who is Rachel Carson and what was Silent Spring?
- journalist
- documented the environmental harm cause by the indiscriminate use of DDT, a pesticide used by soldiers during WW2 to control malaria/typhus
- described death of birds from spraying DDT to control mosquitoes
- argued that pesticides including DDT were poisoning both wildlife and the environment and were endangering human health
what does DDT do in predatory birds?
- affected offspring
- caused by DDE (break-down product of DDT)
- blocks calcium carbonate production (calcium metabolism) = resulted in eggshell thinning, eggs would be crushed when sat on by the mother birds
- results in severe population declines for bald eagles, peregrine falcons, and other birds
what are persistent organic pollutants (POPs)?
organic substances that are:
- toxic
- persistent
- bioaccumulate
- prone to long range transport via atmospheric transport and deposition
- likely to cause significant adverse human health or environmental effects near to and distant from their sources
why did canada join the stockholm convention?
POP contamination found in relatively pristine arctic regions. discovered that inuit were the most contaminated humans - inuit people consumed high numbers of marine mammals, which were highly contaminated
what is the stockholm convention?
in 1995, the governing council of UNEP called for global action to be taken on POPs. an international environmental treaty was signed that aimed to eliminate or restrict the production and use of POPs
what were the dirty dozen?
the 12 POPs that were the worst offenders. the Stockholm Convention focused on these pesticides, industrial chemicals, and by-products for the initial treaty.
what chemicals were a part of the dirty dozen, and what restrictions were placed on them?
Annex A (elimination): aldrin, chlordane, dieldrin, endrin, heptachlor, hexachlorobenzene, mirex, toxaphene, PCB
Annex B (restriction): DDT
Annex C (unintentional production/release): polychlorinated dibenzo-p-dioxins and dibenzofurans, hexachlorobenzene, PCB
how many new chemicals have been added to the stockholm convention?
16 additional POPs have been added by 181 parties as of 2017
what country hasn’t signed the stockholm convention?
the US, but they’ve banned a number of the chemicals
what is the shortcoming of the implementation of a chemical regulation approach like the stockholm convention?
- it is reactionary, not precautionary
- substances are only added after exposure and ecological harm has been demonstrated through environmental and laboratory observations, often long after the first awareness of red flags
how many chemicals are known?
140 million are known and assigned Chemical Abstracts Service (CAS) registry numbers. 211,934 chemicals were known and assigned CAS RNs when Silent Spring was published. over 350,000 chemicals have been registered for production and use
what is canada’s domestic substances list (DSL)?
- an inventory of substances manufactured in, or imported into Canada on a commercial scale
- ~28,000 substances
- vast majority have not been measured in environmental media and their emissions and fast are unknown
- substances not on the DSL are considered new to Canada
- prior to being imported or manufactured over certain threshold, they must be assessed to determine if they are toxic or could become toxic
why are there delays with toxicity testing substances that are on the DSL?
- ~1000 new substances need to be assessed each year
- currently, toxicity testing for a single chemical can cost upwards of $20 million USD and can take up to 4 years
what is CEPA?
- canadian environmental protection act, 1999
- jointly administered by ECCC and HC
- primary tool for assessing and managing chemical substances in the environment
- CEPA 1999 requires that every new chemical substance made in Canada or imported from other countries since 1994 be assessed against specific criteria
CEPA, 1999 requires that chemicals on the DSL be subject to a two-phase evaluation:
1) a hazard assessment in which chemicals are evaluated against persistence (P), bioaccumulation (B), and toxicity (T) endpoint criteria
2) hazardous candidates are then subject to more comprehensive evaluations including risk assessments
there are over ____ laws covering:
25, human health and environmental issues
a risk assessment is generally used to determine if a new chemical poses a risk. it usually involves one or more of:
- review academic and/or industry data
- computer modeling
- carry out LC50 acute and chronic exposures on indicator species
- studies would also be conducted to identify the likely fate of the toxicant in the environment and thus predict exposure concentrations
what happens if a chemical has already reached the environment and there is a concern, but there hasn’t been tests conducted on it?
a retrospective risk assessment is conducted
how is environmental harm determined?
the risks posed by a substance are determined both by its hazardous properties and by the nature of the exposure that takes place
according to CEPA 1999, a substance is toxic if it is entering or may enter the environment in a quantity or concentration or under conditions that:
1) have or may have an immediate or long-term harmful effect on the environment or its biological diversity
2) constitute or may constitute a danger to the environment on which life depends on
3) constitute or may constitute a danger in canada to human life or health
