Flashcards
Sue L2: Toxicity
Flashcards do conjunto (41)
- 1What is a toxin?A substance in a quantity of dose that exceeds the body's ability to deal with it without harm
--> virtually any substance is toxic if taken in a large enough dose - 2What are the toxins that legislation focuses on?-the MOST toxic, i.e.:
-toxic in small amounts
-can bioaccumulate (e.g. in filter feeders such as mercury and lead)
-can biomagnify (e.g. DDT wiping out birds of prey)
-persistent (hard to break down, e.g. PCBs)
-carcinogenic
-mutagenic - 3How do toxins build up in the body?Can be:
-cumulative (absorbed into the body and excreted slowly so conc. builds up, e.g. lead)
-non-cumulative (absorbed but excreted quickly e.g. alcohol - effects still may be cumulative over time)
-acute (such as CYANIDE, immediate effect)
-chronic (effects take >14 days) - 4How do the EU classify toxins?Toxins of most concern are placed onto LIST 1, contains substances that are:
"so toxic, persistent or bio-accumulative in the environment that pollution by them should be eliminated"
-e.g. organochlorides, mercury - 5What are the regulations for major toxins in the EU?-The PIC (PRIOR INFORMED CONSENT) regulation
-REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) directive 2007 - 6PRIOR INFORMED CONSENT regulationcovers the import and export of certain hazardous chemicals and places obligations on companies who wish to export these chemicals to non-EU countries. This includes POPs defined under the Stockholm convention
- 7REACH directive:REACH applies to substances manufactured or imported into the EU in quantities of 1 tonne or more per year
-makes industry responsible for assessing and managing the risks posed by chemicals and providing appropriate safety info. to users
-companies importing chemicals and products in to the EU need to demonstrate their safety - 8What are POPs?POPs: Persistent Organic Pollutants defined by UN as:
-chemical substances that persist in the environment, bioaccumulate through the food web, and pose a risk of causing adverse effects to human health and the environment
-there is evidence of long-range transport of POPs, have been found in regions, such as ALASKA, where they are not produced yet accumulate in fatty tissues of marine mammals as they are lipophilic - 9Because of POPs ability for long-range transport...what measures were put in place?1995, UN called for global action to be taken on POPs, resulting in the STOCKHOLM CONVENTION entering into force in 2004
- 10The Stockholm Convention:2004: initially with 128 parties and originally focussing on 12 POPs (the dirty dozen) mostly organochlorides (e.g. PCBs, dioxins)
2010: 22 POPs - 11EU POPs regulations updated 2010-BAN or RESTRICT the PRODUCTION, USE and SALE of listed POP chemicals
-Require efforts to MINIMISE the FORMATION of UNINTENTIONAL persistent organic BY-PRODUCTS
-Describe how STOCKPILES of POPs must be managed - 12POP categories:As of 2010, 22 POPs fall into 3 categories:
1. PESTICIDES (e.g. DDT)
2. INDUSTRIAL CHEMICALS (e.g. PCBs)
3. Unintentionally produced by-products (e.g. dioxins -by-products of combustion) - 13EOPs:Emerging Organic Pollutants are a more recent group of yet unregulated organic contaminants inc.:
-Bisphenol A from non-stick coatings on pans which can gradually be washed into waterway and exhibits oestrogen-mimicking properties (In February 2017, France proposed BPA as a REACH Regulation candidate 'substance of very high concern')
-pharmaceuticals - 14Examples of pharmaceuticals as EOPs:-contraceptives
-ibuprofen
-anti-depressants
major example:
--DICLOFENCAC - 15DICLOFENAC-is an anti-inflammatory given to cattle in India to reduce suffering (killing not allowed for religious reasons)
-Critically Endangered vultures scavenge on dead carcasses -DICLOFENAC was deemed the primary cause of popn decline (lethal to vultures)
-->BANNED in 2006 but 36% of >250 pharmacies studied (2011) still selling it
-->vulture safety in the wild can't be guaranteed until diclofenac stops being produced - 16Problems specifically with pharmaceuticals entering waterways:-Pharmaceuticals, in contrast to most other chemicals, are BIOLOGICALLY-ACTIVE, they are made to affect biological processes
-therefore they are going to affect biological processes in other species too - 17How do pharmaceuticals enter the environment?People throw them in bins or flush down the toilet rather than returning to pharmacy
-For some drugs the FDA recommends flushing down the toilet if they are risky to human-health to lie around - 18USE of drugs being released example:feminised male fish have been found downstream of sewage plants due to synthetic oestrogen excreted by women taking contraception
-Canadian research tested this on a whole ecosystem by dosing an entire lake with oestrogen to a conc. of 5 nanograms/litre over several years (only slightly over treated sewage levels)
-->FATHEAD MINNOW almost completely eradicated after 3 years of treatment as it had worked as a contraceptive - 19PRODUCTION of drugs example:India has a lot of pharmaceutical industries and water surrounding these has up to 1 million times higher levels of pharmaceuticals than normal levels
NOT JUST INDIA's problem:
-sold globally, moral responsibility to solve the problem
-massive release of antibiotics into env. risks stimulating development of antibiotic resistant bacteria (one of the three biggest threats to public health -WHO) - 20What are the issues related to drug production?1. There are NO LIMITS on the amount of drugs a factory can flush out (very valuable so presumed they don't let much out)
2. Greater transparency is needed: no way of knowing where a drug was made ('produced in..' only relates to the final product)
3. There is a LACK of INCENTIVE to invest in GREEN production (e.g. subsidies, requirements for pollution control)
4. There is a NEED FOR GLOBAL COORDINATION (it matters v little WHERE antibiotic resistance arises) - 21EU protection of natural water?The WATER FRAMEWORK DIRECTIVE 2000
-Was designed to protect water ecology and had to be implemented by all member states of the EU
-defines an Environmental Quality Standard (EQS) for the chemicals with most potential to cause harm
-EQS is a limit where there is "no harm" to humans - 22What are the difficulties in setting "safe limits"?-variations btwn species (e.g. EQS are set for protection of human health but would have different effects on other forms of aquatic life)
-response of an organism may change according to size, age, sex (come chemicals mimic sex hormones, e.g. Bisphenol A). - 23Interactions between toxins?A problem of wastewater effluents is that they are often mixtures:
-ADDITIVE (if 2 or more are present, they may exert a combined effect)
-ANTAGONISTIC (may interfere with each other e.g. calcium is antagonistic to (reduces) the toxicity of zinc, aluminium and lead
-SYNERGISTIC (the combined effect is more than the two combined e.g. aluminium is not toxic unless in pH 5-5.5)
-VARIABLE (copper is antagonistic with cyanide but additive with lead) - 24How can this mixture of effects be solved?EA may use whole effluent testing (e.g. using Microtox)
-also gets over the problem of setting limits for substances which may only be present in small amounts - 25What is MICROTOX?Is a BIOASSAY SYSTEM for detection and measurement of toxicity
-uses luminescent marine bacteria, such as PHOSPHOREUM, which are sensitive to a broad spectrum of toxic chemicals
-the microorganisms emit light as a natural product of their metabolism, when TOXINS ARE PRESENT, the light output drops in proportion to the toxicity of the sample
-light measurements are taken and analysed by a computer automatically - 26Advantages/Disadvantages of microtox bioassays:Advantages: relatively cheap, quick, portable and can be useful for other things such as checking the efficacy of sewage treatment; suggesting the source of a pollutant by taking samples as you move down the river and ID where light output is most reduced
Disadvantages: sensitivity varies btwn species (should test each trophic levels- microorganisms, inverts. verts.); does not tell you WHAT THE TOXIN IS. - 27What are the factors affecting toxicity?-Temperature (rise of 10C halves survival time)
-Transformation (may transform in an aquatic system, e.g. inorganic mercury converted to v.toxic methyl mercury (e.g. Minamata, methyl mercury entered food chain leading to mercury poisoning in residents)
-Biomagnification up the food chain
-Bioaccumulation (e.g. freshwater snail LYMNEAE PALUSTRIS can concentrate LEAD by 300,000 times)
-Tolerance can build up, particularly where popn reproduce quickly
-Potentiation occurs when previous exposure to a toxin can increase sensitivity next time, e.g. ORGANOPHOSPHATES - 28What are the effects of toxins?-death
-immune system may be affected
-respiratory system may be affected
-reproductive system may be affected
-nervous system may be affected
-change in behaviour
-birth defects
-cancer - 29How can we determine what a safe level of a toxin is?Toxicity testing - usually takes place in the lab, organisms should be same age, sex etc.
-can use DEATH as a criteria or monitor a PHYSIOLOGICAL RESPONSE, e.g. HR to test CHRONIC effects
-Common test spp. is rainbow trout - 30What results can you get from toxicity testing?-Lethal Concentration (LC)
-Effective Concentration (EC)
-Incipient Lethal Level or Incipient TLm
-Safe concentration - 31-Lethal Concentration?Where death is the criterion of toxicity. The results are expressed with a number (which indicates the percentage of animals killed at a particular concentration in a set amount of time
e.g. 48-h LC70: is the concentration of toxin which kills 70% of the test organisms in 48 hours - 32-Effective Concentration?The term used when an effect other than death is being studied, e.g. HR
Results expressed in a similar way
e.g. 48-h EC50: the concentration at which there is a 50% drop in photosynthesis/HR etc - 33Incipient Lethal Level or Incipient TLm?The concentration at which ACUTE TOXICITY CEASES, usually taken as the concentration at which 50% of the popn of test organisms can live for an indefinite time
- 34Safe Concentration?The max. conc. of a toxic substance that has no observable effects on a species after LONG-TERM EXPOSURE over ONE OR MORE GENERATIONS
- 35Convert incipient lethal level to a safe concentration?APPLICATION FACTORS are used to convert from the incipient TLm to the safe permissible conc.
In the case of ACUTE poisons, the ITLm is usually divided by 10
and in CHRONIC toxicity, by 1000
ie if the ITLm was 10 mg/l then you would set a limit of 1 mg/l for an acute toxin and 0.01 for a chronic toxin - 36How can we avoid toxicity issues?-BAN the most dangerous chemicals
-Find ALTERNATIVES e.g. lead free solder, less persistent pesticides
-recycle chemicals within CLOSED LOOP systems so they can't get into environment
-ensure hazardous chemicals are DISPOSED of appropriately (e.g. incinerated)
-adopt the PRECAUTIONARY PRINCIPLE: if in doubt, don't use the chemical (led to REACH Directive where the onus is now on importing company to prove chemical is safe rather than EA to prove it is dangerous)
-REGULATE - problem is POPs are transboundary but not all countries sign up. - 37Examples of POPs:-DDT
-PCBs
-dioxins and furans - 38-DDT?INSECTICIDE used on agricultural crops, primarily cotton, and insects that carry diseases such as malaria
- 39DDT case study:BERG ET AL. 1992:
-DIFFUSE source + biomagnification in LAKE KARIBA, along border btwn ZIMBABWE and ZAMBIA is the largest man-made lake and reservoir by volume
-Diverse, aquatic ecosystem with many fish, crocodiles, birds, hippopotamus
-Pesticides were widely used across Zimbabwe in 1960s such as DDT (kills mosquitos carrying malaria) - over 100 tonnes of DDT sprayed around Kariba area
-DDT sinks to river bed --> biomagnification
-Crocodiles 34,000 ppm DDT
-DDT phased out and other methods had to be used for malaria, nets etc - 40-PCBs?Used for a variety of industrial processes and purposes, inc in transformers, as paint additives and in plastics
-also unintentionally produced during combustion - 41-dioxins and furans-unintentionally produced during most forms of combustion, including burning of municipal and medical wastes, backyard burning of trash
-also can be found in certain herbicides and wood preservatives
Informações
- Descrição
- Pollution of Air, Water and Soil 2 (Water Pollution) FlashCards sobre Sue L2: Toxicity, criado por Phoebe Stockton em 27-05-2017.
- Criado por
- Phoebe Stockton
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