Lexikon

standard phrases relating to the safe use of dangerous chemical substance. For example "Keep container tightly closed" or "avoid contact with skin" or "do not empty into drains". When the current provisions are repealed and GHS enters into force, the S-phrases will be replaced by "precautionary statements". (Source: REACH Glossary).

The S-phrases are enlisted under the entry of "safety advice for the use of dangerous substances".

safety is the state of being "safe" (from French sauf), the condition of being protected against physical, social, spiritual, financial, political, emotional, occupational, psychological, educational or other types or consequences of failure, damage, error, accidents, harm or any other event which could be considered non-desirable. Safety can also be defined to be the control of recognized hazards to achieve an acceptable level of risk. This can take the form of being protected from the event or from exposure to something that causes health or economical losses. It can include protection of people or of possessions.

In environmental science and management chemical safety has priority importance. Chemical safety means that the risk of hazardous chemical substances on humans or ecosystem is reducen onto an acceptable level.

Source: http://en.wikipedia.org/wiki/Safety

European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. The list was consolidated and republished in Directive 2001/59/EC.

Simple phrases

(S1): Keep locked up

(S2): Keep out of the reach of children

S3: Keep in a cool place

S4: Keep away from living quarters

S5: Keep contents under ... (appropriate liquid to be specified by the manufacturer)

S6: Keep under ... (inert gas to be specified by the manufacturer)

S7: Keep container tightly closed

S8: Keep container dry

S9: Keep container in a well-ventilated place

S10: Keep contents wet

S11: Avoid contact with air

S12: Do not keep the container sealed

S13: Keep away from food, drink and animal foodstuffs

S14: Keep away from ... (incompatible materials to be indicated by the manufacturer)

S15: Keep away from heat

S16: Keep away from sources of ignition - No smoking

S17: Keep away from combustible material

S18: Handle and open container with care

S20: When using do not eat or drink

S21: When using do not smoke

S22: Do not breathe dust

S23: Do not breathe gas/fumes/vapour/spray (appropriate wording to be specified by the manufacturer)

S24: Avoid contact with skin

S25: Avoid contact with eyes

S26: In case of contact with eyes, rinse immediately with plenty of water and seek medical advice

S27: Take off immediately all contaminated clothing

S28: After contact with skin, wash immediately with plenty of ... (to be specified by the manufacturer)

S29: Do not empty into drains

S30: Never add water to this product

S33: Take precautionary measures against static discharges

S35: This material and its container must be disposed of in a safe way

S36: Wear suitable protective clothing

S37: Wear suitable gloves

S38: In case of insufficient ventilation wear suitable respiratory equipment

S39: Wear eye/face protection

S40: To clean the floor and all objects contaminated by this material use ... (to be specified by the manufacturer)

S41: In case of fire and/or explosion do not breathe fumes

S42: During fumigation/spraying wear suitable respiratory equipment (appropriate wording to be specified by the manufacturer)

S43: In case of fire use ... (indicate in the space the precise type of fire-fighting equipment. If water increases the risk add - Never use water)

S45: In case of accident or if you feel unwell seek medical advice immediately (show the label where possible)

S46: If swallowed, seek medical advice immediately and show this container or label

S47: Keep at temperature not exceeding ... °C (to be specified by the manufacturer)

S48: Keep wet with ... (appropriate material to be specified by the manufacturer)

S49: Keep only in the original container

S50: Do not mix with ... (to be specified by the manufacturer)

S51: Use only in well-ventilated areas

S52: Not recommended for interior use on large surface areas

S53: Avoid exposure - obtain special instructions before use

S56: Dispose of this material and its container at hazardous or special waste collection point

S57: Use appropriate containment to avoid environmental contamination

S59: Refer to manufacturer/supplier for information on recovery/recycling

S60: This material and its container must be disposed of as hazardous waste

S61: Avoid release to the environment. Refer to special instructions/safety data sheet

S62: If swallowed, do not induce vomiting: seek medical advice immediately and show this container or label

S63: In case of accident by inhalation: remove casualty to fresh air and keep at rest

S64: If swallowed, rinse mouth with water (only if the person is conscious)

Combinations

(S1/2): Keep locked up and out of the reach of children

S3/7: Keep container tightly closed in a cool place

S3/7/9: Keep container tightly closed in a cool, well-ventilated place

S3/9/14: Keep in a cool, well-ventilated place away from ... (incompatible materials to be indicated by the manufacturer)

S3/9/14/49: Keep only in the original container in a cool, well-ventilated place away from ... (incompatible materials to be indicated by the manufacturer)

S3/9/49: Keep only in the original container in a cool, well-ventilated place

S3/14 Keep in a cool place away from ... (incompatible materials to be indicated by the manufacturer)

S7/8: Keep container tightly closed and dry

S7/9: Keep container tightly closed and in a well-ventilated place

S7/47: Keep container tightly closed and at temperature not exceeding ... °C (to be specified by the manufacturer)

S20/21: When using do not eat, drink or smoke

S24/25: Avoid any inhalation, contact with skin and eyes. Wear suitable protective clothing and gloves

S27/28: After contact with skin, take off immediately all contaminated clothing, and wash immediately with plenty of ... (to be specified by the manufacturer)

S29/35: Do not empty into drains; dispose of this material and its container in a safe way

S29/56: Do not empty into drains, dispose of this material and its container at hazardous or special waste collection point

S36/37: Wear suitable protective clothing and gloves

S36/37/39: Wear suitable protective clothing, gloves and eye/face protection

S36/39: Wear suitable protective clothing and eye/face protection

S37/39: Wear suitable gloves and eye/face protection

S47/49: Keep only in the original container at temperature not exceeding ... °C (to be specified by the manufacturer)

safety at work is widely accepted as the authoritative guide to safety and health in the workplace and covers all aspects of safety management.

the safety data sheet is the main tool used in industry for communicating information on the hazard of dangerous substances and preparations through the supply chain. Annex II of REACH is based on the Annex to the safety data sheet Directive (91/155/EEC) and explains what information should be included under each of the 16 safety data sheet headings. (Source: REACH Glossary)

Strategic Approach to International Chemical Management (SAICM) adopted on 6 February 2006 in Dubai.

SAICM supports the achievement of the goal agreed at the 2002 Johannesburg World Summit on Sustainable Development of ensuring that, by the year 2020, chemicals are produced and used in ways that minimize significant adverse impacts on the environment and human health.

Source: http://www.saicm.org/index.php?ql=h&content=home

the process through which fresh (drinkable) water becomes salt (undrinkable) water; hence, desalination is the reverse process; also involves the accumulation of salts in topsoil caused by evaporation of excessive irrigation water, a process that can eventually render soil incapable of supporting crops.

Soil salination is a process that may result from: 1. high levels of salt in the soils; 2. landscape features that allow salts to become mobile, 3. climatic trends that favor accumulation, 4. human activities such as land clearing and aquaculture activities.

a portion or piece of a whole. A selected subset of a population or subset of whatever is being studied. For example, in a study of people the sample is a number of people chosen from a larger population. An environmental sample (for example, a small amount of soil or water) might be collected to measure contamination in the environment at a specific location.

The sample should truly represent the population or environment is being studied. It is ensured by statistically suitable sample size and sample and sample type.

To collect a representative sample-set from the environment we have to design sampling carefully. In case of contaminated sites our sampling should be based on the risk of the contaminant and on the integrated risk model or conceptual model of the site.

the scale problem is due to the spatiotemporal (i.e., in space and in time) variability of the systems of interest: statements that concern a particular scale may (and often will) not hold at other scales. Hence, extrapolation of understanding to a larger or to a smaller scale may require additional knowledge at these larger or smaller scales. (Source: EUGRIS)

Scientific Committee on Emerging and Newly Identified Health Risks, one of the scientific committees of the Europian Commission.

It shall provide opinions on questions concerning emerging or newly identified health and environmental risks and on broad, complex or multidisciplinary issues requiring a comprehensive assessment of risks to consumer safety or public health and related issues not covered by other community risk assessment bodies.

Examples of potential areas of activity include potential risks associated with interaction of risk factors, synergic effects, cumulative effects, antimicrobial resistance, new technologies such as nanotechnologies, medical devices including those incorporating substances of animal and/or human origin, tissue engineering, blood products, fertility reduction, cancer of endocrine organs, physical hazards such as noise and electromagnetic fields (from mobile phones, transmitters and electronically controlled home environments), and methodologies for assessing new risks. It may also be invited to address risks related to public health determinants and non-transmissible diseases.

http://ec.europa.eu/health/ph_risk/committees/04_SCENIHR/04_SCENIHR_en.htm

in sedimentology sediment is any particulate matter (inorganic or organic) that comes from the weathering of rock and can be transported by water (fluvial processes), by wind (aeolian processes) and by glaciers and which eventually is deposited. The sediment can be classified based on its grain size and/or its composition. Sediment size is measured on a log base 2 scale, called the "Phi" scale, which classifies particles by size from "colloid" to "boulder". Composition of sediment can be measured in terms of: parent rock lithology, mineral composition, chemical make-up. The sediment is transported based on the strength of the flow that carries it and its own size, volume, density, and shape. Sediment motion can create self-organized structures such as ripples, dunes, antidunes on the river or stream bed. These bedforms are often preserved in sedimentary rocks and can be used to estimate the direction and magnitude of the flow that deposited the sediment. When the ground surface is stripped of vegetation and then seared of all living organisms, the upper soils are vulnerable to both wind and water erosion. In a number of regions of the earth, entire sectors of a country have become erodible. Loss of soil due to erosion adds to sediment loads in the river systems.

See also surface water sediments

natural sediments are defined as the organic and inorganic materials found at the bottom of a water body. Sediments may include clay, silt, sand, gravel, decaying organic matter, and shells among other things, but exclude anthropogenic debris, such as vehicle tires.

Sediments can become contaminated in a number of ways. Urban runoff that discharges to surface waters often contains polycyclic aromatic hydrocarbons (PAHs), oil and grease, and heavy metals. Agricultural runoff may contain nutrients and pesticides. Industrial spills and releases, especially those that occurred before controls were in place, can put product into the water. Chemicals that are denser than water, such as polychlorinated biphenyls (PCBs) and some pesticides like DDT, will sink to the bottom of water bodies and directly contaminate sediments. Atmospheric deposition of substances such as mercury is another source of sediment contamination as is the discharge of contaminated groundwater through the sediments to the overlying surface water (USEPA 1999 and USEPA 2005).

The classes of contaminants that are most common in sediment contamination are pesticides, PCBs, PAHs, and to a lesser extent dissolved phase chlorinated hydrocarbons. With the right geochemical conditions heavy metals and metalloids can also occur in sediments or precipitate into them. The sediments of many marinas are contaminated with tributyltin, an organo tin compound that was used as a biocide in marine paints (USEPA 1999).

Sediment investigations are generally conducted in two parts. The first uses common sampling and analytical procedures to determine if the total concentrations of contaminants are high enough to warrant concern. The underlying assumption is that all the contaminant is bioavailable. If the data indicate there may be a problem, then the second part of the investigation is done. This part focuses on bioavailability and determining whether there is physical evidence of an impact such as less biodiversity in the impacted sediments and the presence of the chemicals in the tissue of flora and fauna (USEPA 2005).

In addition to evaluating contaminant concentrations, the site investigation needs to develop a very complete conceptual site model. Unlike conventional soil and groundwater investigations, where rapid change in the site conditions is not expected, sediment systems can be very dynamic and it is important for both the risk assessment and remedy selection to have a full understanding of potential changes in site dynamics. A fuller discussion on investigation techniques is found in the Site Characterization section (USEPA 2005).

The risk assessment estimates the potential impacts of the contaminated sediments on human and ecological receptors. Many common organic sediment contaminants are suspected carcinogens and some, such as PCBs and mercury, bioaccumulate in the food chain. Risk assessors have developed a triad, or weight-of-evidence approach, that integrates sediment chemistry, laboratory toxicity testing, and community structure indices to assess risk (Pinkney et al 2005). A more complete discussion of sediment risk assessment and related guidance documents can be found in the Risk Assessment section.

Sources:

USEPA. 1999. Introduction to Contaminated Sediments. EPA 823-F-99-006, Office of Science and Technology, 24 pp.

USEPA. 2005. Adobe PDF LogoContaminated Sediment Remediation Guidance for Hazardous Waste Sites, EPA-540-R-05-012. Office of Superfund Remediation and Technology Innovation, 236 pp.

Pinkney, A.E., B.L. McGee, P.C. McGowan, D.J. Fisher, J. Ashley, and D. Velinsky. 2005. Adobe PDF LogoUsing the Sediment Quality Triad Approach to Characterize Toxic Conditions in the Chesapeake Bay (2002): An Assessment of Tidal River Segments in the Bohemia, Elk, Northeast and Severn Rivers, CBFO-C05-01. USEPA, Chesapeake Bay Program Office, 234 pp.

sedimentary rock is the type of rock that is formed by sedimentation of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution. Particles that form a sedimentary rock by accumulating are called sediment. Before being deposited, sediment was formed by weathering and erosion in a source area, and then transported to the place of deposition by water, wind, mass movement or glaciers. Though sedimentary rocks form just a small part of the Earth's crust, they cover the largest part of the Earth's surface. Sedimentary rocks are deposited in strata that form a structure called bedding. Sedimentary rocks contain important information about the history of Earth. They contain fossils, the preserved remains of ancient plants and animals. The composition of sediments provides us with clues as to the original rock. Differences between successive layers indicate changes to the environment which have occurred over time. Sedimentary rocks can contain fossils because, unlike most igneous and metamorphic rocks, they form at temperatures and pressures that do not destroy fossil remains. (http://en.wikipedia.org/wiki). Sedimentary rocks are classified into three groups. These groups are: clastic, chemical precipitate and biochemical or biogenic. Clastic sedimentary rocks are composed of discrete fragments or clasts of materials derived from other minerals. They are composed largely of quartz with other common minerals including feldspar, amphiboles, clay minerals, and sometimes more exotic igneous and metamorphic minerals. The classification of clastic sedimentary rocks is complex because there are many variables involved. Particle size (both the average size and range of sizes of the particles), composition of the particles, the cement, and the matrix (the name given to the smaller particles present in the spaces between larger grains) must all be taken into consideration. (http://en.wikipedia.org/wiki). Chemical sedimentary rocks form when minerals in solution become oversaturated and precipitate. In marine environments, this is a method for the formation of limestone. Another common environment in which chemical sedimentary rocks form is a body of water that is evaporating. Evaporation decreases the amount of water without decreasing the amount of dissolved material. Therefore, the dissolved material can become oversaturated and precipitate. Sedimentary rocks from this process can include the evaporite minerals halite (rock salt), barite and gypsum (http://en.wikipedia.org/wiki). Organic sedimentary rocks contain materials generated by living organisms, and include carbonate minerals created by organisms, such as corals, mollusks, and foraminifera, which cover the ocean floor with layers of calcite which can later form limestone. Other examples include coal and oil shale (derived from the remains of tropical plants and subjected to heat) (http://en.wikipedia.org/wiki).

a senzitiezer is a dangerous chemical substance that causes a substantial proportion of exposed people or animals to develop an allergic reaction in normal tissue after repeated exposure to the chemical substance. Certain sentisizers have no immediate health effects. But if an organism is exposed to them several times, an allergic reaction may arise. A sensitizer may make an organism sensitive to other chemicals too, often quite suddenly. Typical reactions to sensitizers can include skin disorders such as eczema, respiratory disorders such as asthma, skin irritation (ulticaria), etc. Being under the effect of a sensitizer is also called hypersensitivity.

Sensitization is an immune response. Therefore, some people may be easily sensitized while others may never be affected. Like any allergic response, a reaction to a sensitizer can be fatal in rare circumstances. You can not predict your reaction to sensitizing chemicals, so treat all sensitizers with great respect and follow proper chemical safety and hygiene procedures.

according to REACH definition, an eye damage is serious the production of tissue damage in the eye, or serious physical decay of vision, following application of a test substance to the anterior surface of the eye, which is not fully reversible within 21 days of application.

The Society of environmental toxicology and Chemistry is a not-for-profit, worldwide professional organization comprised of individuals and institutions dedicated to the study, analysis and solution of environmental problems, the management and regulation of natural resources, research and development and environmental education. Our mission is to support the development of principles and practices for protection, enhancement and management of sustainable environmental quality and ecosystem integrity.
SETAC fulfills its mission through the advancement and application of scientific research related to contaminants and other stressors in the environment, education in the environmental sciences and the use of science in environmental policy and decision-making.
http://www.SETAC.org/

SETAC Europe is a Geographic Unit (GU) of the Society of environmental toxicology and Chemistry (SETAC), established to promote and undertake activities of SETAC in Europe. SETAC Europe is dedicated to the use of multidisciplinary approaches to examine the impacts of stressors, chemicals, and technology on the environment. The Society also provides an open forum for scientists and institutions engaged in the study of environmental problems, management and regulation of natural resources, education, research and development, and manufacturing.
http://www.SETAC.org/node/88

A value for the characterisation of plant diversity.
H = - Σ (ln Pi) * Pi. Pi = Ni / Σ Ni, Ni = number of plant within a species or other taxa.

see 1013/2006/EC regulation on shipment of waste

the silicate minerals make up the largest and most important class of rock-forming minerals, comprising approximately 90 percent of the crust of the Earth. Silicate minerals all contain silicon (silicium in Latin) and oxygen. They are classified based on the structure of their silicate group. The most predominant silicate is quartz (SiO₂). The basic chemical unit of silicates is the (SiO₄) tetrahedron shaped anionic group with a negative four charge (^-4). The central silicon ion has a charge of positive four while each oxygen has a charge of negative two (^-2) and thus each silicon-oxygen bond is equal to one half (1/2) the total bond energy of oxygen. This condition leaves the oxygens with the option of bonding to another silicon ion and therefore linking one (SiO₄) tetrahedron to another and another, etc. Mineralogically, silicate minerals are divided according to structure of their silicate anion into the following groups: nesosilicates (single tetrahedrons), sorosilicates (double tetrahedrons), inosilicates (single and double chains), cyclosilicates (rings), phyllosilicates (sheets), tectosilicates (frameworks).The phyllosilicates (sheet silicates) include the clay minerals. They are one of the primary products of chemical weathering and one of the more abundant constituents of sedimentary rocks. The basic structure of the phyllosilicates is based on interconnected six member rings of SiO₄^-4 tetrahedra that extend outward in infinite sheets. Three out of the 4 oxygen atoms from each tetrahedon is shared with other tetrahedra. This leads to a basic structural unit of Si₂O₅^-2. In case the Si⁺⁴ atom in the middle of the tetradera is replaced by lower valency atoms such as Fe⁺³ or Al⁺³, then more negative bonds become available on the surface of the sheet structured clay minerals (http://en.wikipedia.org). These bonds have primary role in plant nutrient fixation, exchange and supply. Meanwhile these bonds contribute to the sorption of inorganic contaminants, fixing of ions to the surface of the clay mineral, while in case of treatment of contaminated soil to their removal (soil washing, extraction) or even to their stabilisation (soil stabilisation, immobilisation, chemical immobilisation/stabilisation in soil, vitrification). See also fate of inorganic pollutants in soil.

occurs when water channels and reservoirs become clotted with silt and mud, a side effect of deforestation and soil erosion.

Simple-box model is a nested multimedia fate model for evaluating the environmental fate of chemicals.

SimpleBox is a nested multimedia box model of the "Mackay type". The environment is modeled as consisting of a set of well-mixed homogeneous compartments (air, fresh water, sea water, sediments, three soil compartments and two vegetation compartments) in regional, continental and global spatial scales. The model takes emission rates and rate constants for transport and transformation of micropollutants as input and computes steady-state concentrations in the environment as output. SimpleBox is a generic model which can be customised to represent specific environmental situations. In its default setting, the SimpleBox computation represents the behaviour of micropollutants in a regional and continental spatial scale; representing a densely populated Western European region, and the whole of the European Union, respectively. The 2.0 version of the model was produced as a starting point for a project aimed at validation of the intended use of the model in harmonisation of environmental quality objectives of air, water, and soil in the Netherlands. SimpleBox 2.0 has also served as a basis for the regional/continental distribution module into the European Union System for Evaluation of Substances (EUSES).

SimpleTreat isa model to predict the distribution and elimination of Chemicals by Sewage Treatment Plants.

The SimpleTreat 3.0 is a model to predict the distribution and elimination of chemicals by sewage treatment. SimpleTreat 3.0 is an improved version of SimpleTreat, applied in the Netherlands in the Uniform System for the Evaluation of Substances (USES version 1.0, 1994). Although in the very beginning strong reservations were encountered, the model has become accepted as a useful tool for generic exposure assessment. It is now recognized that the accuracy of exposure assessment, in particular for the water compartment in urban regions, is largely determined by the accuracy with which the chemical fate in sewage treatment plants (STP) can be predicted. This model includes a wider range of operation modes of wastewater purification to account for the variety of communal wastewater scenarios across the EU. Chemical transport and transformation processes also cover a wider range of applications both for compound properties and scenarios. Emission of substances via sludge production was modified to account for the presence and absence of primary sedimentation. The first scenario applies to the urban areas where usually large installations purify the raw wastewater ; the second is more representative for rural regions, where a high percentage of the wastewater goes through treatment installations, for example in Denmark. Mathematical expressions of individual processes, which chemicals may undergo in a STP were critically reviewed. Emission to the air compartment, due to stripping in the aeration tank, has been re-assessed by taking into account the gas-phase resistance. This correction is necessary to better predict the behaviour of semi-volatile chemicals. However, the input of biodegradation data and the way this information is processed have been altered the most. Modifications are partly motivated by the discussions in the course of developing a risk assessment system for "new" and "existing" chemicals in the European Community. Also, results, presented in recent literature, have been implemented. A second version of USES to be applied in the EU, is currently being developed. Since a sewage treatment chemical fate model should cover many scenarios to play its key role in exposure assessment, it was decided to use SimpleTreat 3.0 for this purpose in USES 2.0, instead of SimpleTreat. This report may serve as a reference manual for SimpleTreat 3.0. The electronic version of this spreadsheet file (on accompanying diskette) is written in MicroSoft EXCEL.

(Source: http://rivm.openrepository.com/rivm/handle/10029/10404)

SIN = Substitute it now!

The most effective way to deal with the risk of toxic chemicals problem is to eliminate hazardous substances at the source. This means substituting chemicals of high concern with less dangerous chemicals or with new technologies. Substitution is a proven driver for innovation, leading to the development of products that are more effective and no longer based on dubious chemicals and outdated processes.

Estimates suggest that there are roughly 2000 known SVHCs currently in use in Europe which shoul be substitute with less risky ones.

ChemSec a European Project, in collaboration with NGOs and the companies in the ChemSec Business Group, has developed the SIN (Substitute It Now!) List.

The SIN List 2.0 (updated in May 2011) highlights 378 substances that fulfull the official REACH criteria of Substances of Very High Concern. Today, many leading international companies use the SIN List as a guide in their substitution work.

WHO has also published substitutes for many of the hazardous substances, e.g.

• 1,3-dichloropropene (1,3-D)
• Aldrin
• Benzene
• Bromine
• Cadmium
• Carbon tetrachloride
• Chlordane
• Chloroform
• Chloropicrin
• Chromium (vi)
• Coolants
• Dazomet
• DDT
• Decabromodiphenylether
• Di(2-ethylhexyl)phthalate (DEHP)
• Dieldrin
• Diethyl ether
• Dimethyl formamide
• Dimethyl sulfate
• Dimethyl sulfoxide
• Endrin
• Ethanol
• Ethidium bromide
• Fibres
• Flame retardants
• Formaldehyde
• Generic acids and bases
• Glutaraldehyde
• HCB
• Heptachlor
• hexabromocyclododecane (HBCD)
• Hexane
• hexavalent chromium
• hydrofluoric acid
• hydrogen peroxide
• Insecticides
• Lead
• Lubricants
• Mercury
• Metam sodium
• Methanol
• Methyl bromide
• Methyl iodide
• Methylene chloride
• Mirex
• MTBE
• Ortho-phthalaldehyde (OPA)
• PCB
• Peracetic acid
• Perchloroethylene (PCE)
• Petroleum
• Phenol
• Phosgene
• Phosphorus
• Phthalates
• Plasticisers
• POPs
• Propellants
• PVC
• Pyridine
• Resins
• Separating agents
• Silica
• Sodium borohydride
• Solvents
• Sulfuric acid
• Surfactants (detergents)
• 1,1,1-trichloroethane (TCA)
• Tetrabromobishenol A (TBBPA)
• Tetrahydrofuran
• toluene
• Toxaphene
• tributyltin (TBT)
• Varnish

Read more:

http://www.chemsec.org/get-informed/safer-alternatives

http://www.who.int/ifcs/documents/standingcommittee/substitution/en/index.html

short interfering RNA (siRNA) are short double-stranded RNAs (dsRNA) that can regulate gene expression.

In eukaryotic cells, the enzyme Dicer produces siRNA from small dsRNAs. The siRNA can bind to its complementary messenger RNA (mRNA) and inhibit translation and/or induce the cell to destroy the mRNA. The phenomenon is called RNA inhibition (RNAi), and can be used in the lab to inhibit any gene in any kind of cell (Dove, 2007). "RNA interference has re-energized the field of functional genomics by enabling genome-scale loss-of-function screens in cultured cells" (Echeverri & Perrimon, 2006).

Sources:

Dove, 2007: http://www.dddmag.com/rnai-moves-down-the-pipeline.aspx

Echeverri, C.J. & Perrimon, N. (2006). High-throughput RNAi screening in cultured cells: A user's guide. Nat. Rev. Genet. 7, 373−384.