Understanding Toxicity

• Materials Safety Data Sheets (MSDSs)
• Novel ultra low toxicity thresholds
• How are chemical impacts assessed?
• How to identify Chemicals and their impacts
• Human Health
• Ecological Health issues
• How to determine if a substance or mixture is harmful
• How the ecolabels deal with chemical impacts

 

Human and ecosystem toxicity has generally been inadequately dealt with by the building sector in the past and only becomes a significant focus in an occupational health and safety (OH&S) context for workers in manufacturing of products and sometimes building workers. Legislation is almost silent on a mandate of safe levels of specific problem chemicals in finished products that might affect end users.

Where some attention has been paid to it, only volatile organic compounds (VOCs) and specific chemicals like formaldehyde have been dealt with in any consistent way and these only in Green Star® and more recently by air measurement of finished interiors under the NABERS IEQ (National Building Environment Rating Scheme Indoor Environment Quality) system, While volatile chemicals evaporating out of interior products and being inhaled into the respiratory system is undoubtedly a major influence in human toxicity, there are a whole range of other toxicity pathways, especially dermal (skin) absorption and ecosystem toxicities that we largely ignore (and do so at our peril). The most common source of chemical information on products is the MSDS (material safety data sheet) as all manufacturers are required to produce these sources of information by OH&S legislation.

By examining toxicity over life span (including end-use disposal) as GreenTag does, LCA assesses the total impact of a material on current and future generations in terms of both human and ecosystem health. This is a more complete and balanced approach to those that address important individual issues such as threats to occupant health, sourcing, manufacturing biodiversity impacts or OH&S issues.

While indoor air quality and OH&S are important, considerations currently being addressed by regulators, a range of other critical toxicity pathways such as dermal absorption (skin) and lifecycle ecosystem toxicity including disposal at end of life also require consideration.

Materials Safety Data Sheets (MSDSs)

MSDSs are required to be produced by manufacturers to explain in a standardised format declaring:

i)      the types of chemicals that comprise the product;

ii)     the effects of the finished product on humans and ecosystems;

iii)    safety precautions to take in the event of any accident; and

iv)    the manufacturer's contact details.

MSDSs are required by legislation and are a very useful source of product information. The quality of the data provided in MSDSs varies. Importantly, the impact of the finished product should include its individual components and while this is done through LCA-based product assessment, it is often not undertaken with an MSDS. A product's components can have significant impacts, in their own right, before being combined into a product and as the product breaks down, at end of life.

For example, this is particularly important when we look at highly toxic components (e.g. monomers that are combined to form essentially non-toxic compounds such as polystyrene, epoxy, PVC, synthetic rubber, polyurethane, ABS plastic, etc) where the potential exists for un-reacted or 'free' monomers to exist after the polymerisation reaction, as discussed below.

Novel ultra low toxicity thresholds

Residual free monomer or reactant levels in polymers are an emerging issue in some plastics, as it has been found that some of these chemicals can have significant impacts at much lower levels than previously thought (for example: bisphenol A (BPA) in epoxies and polycarbonates; vinyl chloride monomer (VCM) in PVCs; isocyanate, TDI or MDI monomers in polyurethanes; and styrene monomers in polystyrene, ABS, styrene butadiene rubber (SBR) or synthetic rubber). Care should be taken to ask for the test results of finished products from manufacturers for residual un-reacted monomers when using these products, especially in situations where skin contact is common.

How are chemical impacts assessed?

Chemicals are assessed internationally by a variety of bodies in the European Union (EU) and the USA. Australia has adopted the European system which is based on EU Directive 67/548/EEC. This is related to the United Nations' Globally Harmonized System of Classification and Labelling of Chemicals (GHS), as well as EU Directive 2001/59/E and REACH programs.

These collectively represent the EU Regulation on the 'Classification, Labelling and Packaging of Dangerous Substances and Mixtures' and the related EU ESIS or European Chemical Substances Information System. The system Australia has adopted is called HSIS or 'Hazardous Substances Information System'. [1] HSIS is an internet resource that allows you to find information on substances that have been classified in accordance with the 'Approved Criteria for Classifying Hazardous Substances'. It is currently based on the EU Directive 67/548/EEC and is moving towards the adoption of REACH in the future. In addition to providing powerful search features, HSIS also provides direct access to a consolidated list of all the classified substances contained in the HSIS database. The HSIS database provides searchable access to two data sets, one for hazardous substance information and the other for exposure standard information for human health impacts. While HSIS contains environmental toxicity data, this is not necessarily complete because its focus is on OH&S, so for accuracy ESIS or the GHS systems must also be checked. The HSIS can be searched by use of chemical identifier numbers (called CAS) or UN numbers or alphabetically.

How to identify Chemicals and their impacts

Chemicals can be identified via a number of different pathways. The databases and MSDS will typically include either CAS or UN numbers or both.

'Chemical Abstract Service' Registry Number (CAS Number)

A 'Chemical Abstract Service' Number (CAS Number) is a numerical designation assigned to a single chemical. Mixtures can also be assigned a CAS Number.

United Nations Number (UN Number)

UN Numbers relate to 'Dangerous Goods' classification and are predominantly intended for transport information. The UN number is a four digit catalogue number developed by the UN. They can be assigned to a single substance or to a group with similar characteristics or hazardous properties.

CAS and UN numbers identify the chemical, but to describe the potential impacts of chemicals a variety of indicators such a Risk Phrases (R-Phrases), Safety Phrases (S-Phrases) and 'Toxicity Indicators' are used.

R-Phrases (Risk Phrases)

R-Phrases give a general indication of the potential effect of a chemical. They can be represented by either a number or a phrase (e.g.' R39 Danger of very serious irreversible effects'). They can be listed as single numbers to denote separate statements or with an oblique (/) linking more than one number that denotes a combined statement of the phrases involved in the impacts of a specific substance. [2]

S-Phrases (Safety Phrases)

S-Phrases are indicators of precautions that should be taken when handling a product or its container (e.g. 'S18 Handle and open container with care').

Classification Indicators

There are also a variety of abbreviations used to classify the impacts of products as follows:

C       Corrosive E       Explosive F        Flammable F+ Extremely Flammable N       Dangerous for the Environment

O          Oxidising T          Toxic T+ Very Toxic Xn        Harmful Xi         Irritant

[3]

How to determine if an exposure is dangerous

Toxicity hazard potential is a function of both dose and exposure. The dose measures used are NOAEL and NOAC and they are defined as follows:

NOAELs: 'No Observed Adverse Effect Levels' are the highest doses that don't cause ill-effects. A NOAEL refers to a dose of chemical that is ingested.

NOAECs:  'No Observed Adverse Effects Concentration' is the highest level of a chemical in a toxicity test that did not cause harmful effects to a plant or animal. A NOAEC refers to direct exposure (e.g. through the skin or gills).

While NOAELs and NOAECs are similar, they are not interchangeable. NOAECs and NOAELs are based on tests that determine the lethal concentration or lethal dose (LC or LD) to a given indicator plant or animal, under test conditions, that impact a given percentage of the population. For example, LC₅₀ and LD₅₀ refer to the lethal concentration or dose that kills 50% of a population under test conditions.

The LD50 is generally expressed as the dose in milligrams (mg) of chemical per kilogram (kg) of body weight. LC50 is usually expressed as mg of chemical per volume (e.g. litre or L) of medium (i.e. air or water) which the organism is exposed to. Chemicals are considered highly toxic when the LD50/LC50 is small and practically non-toxic when the value is large. However, the LD50/LC50 does not reflect any effects from long-term exposure (i.e. cancer, birth defects or reproductive toxicity) that may occur at levels below those that cause death. [4]

NOAEL/NOAEC levels or LC/LD toxicity data are not usually, in themselves, able to assess the toxicity risk levels of products in manufacture, use (except for VOCs or similar cases) or disposal without measures or systems for exposure and/or the likelihood or risk of a critical exposure. To assess the exposure thresholds, other measures are used.

TWA (ppm or mg/m³)

The TWA is the 'time-weighted average' concentration for a normal 8-hour workday or 40-hour work week.

STEL (ppm or mg/m3)

The STEL (Short Term Exposure Limit) is the maximum concentration of a substance (a) for a continuous 15-minute exposure period, (b) for maximum of 4 such periods per day, (c) with at least one 60-minute exposure-free period between two exposure periods, and (d) provided the daily TLV-TWA is met. [5]

What are the issues?

Typically each key area of health impact has a 2-4 tier scale of impact in EU or UN based systems:

Human Health

Chemicals in the 'Persistent Organic Pollutants' (POPs) category are banned internationally under the Stockholm Convention. Highly hazardous pesticides and industrial chemicals are also banned under Annexure III of the Rotterdam Convention.

But there are other substances of lesser impacts that have been classified to help us determine the safe levels of exposure for humans and for ecosystems. Below are the major ones likely to be relevant to most home owners and building professionals. They are defined as follows:

Toxicity: To indicate how these are determined, the EU defines chemicals as toxic when they are classified as carcinogenic (category 1A or 1B), mutagenic (category 1A or 1B), or toxic for reproduction (category 1A, 1B, or 2). According to the US EPA the word definitions of toxicity categories are subdivided as follows:

• Category I: Highly toxic; severely irritating
• Category II: Moderately toxic; moderately irritating
• Category III: Slightly toxic; slightly irritating
• Category IV: Practically non-toxic; not an irritant [6]

Some toxins can also be classified as persistent and very persistent, bio-accumulative and very bio-accumulative (see R Phrases).

Carcinogens: Substances capable of causing cancer. Chemicals classified by the 'International Agency on Research into Cancer' (IARC) are:

• Category 1 Carcinogenic to humans
• Category 2A Probably carcinogenic to humans
• Category 2B Possibly carcinogenic to humans
• Category 3A Not classifiable as to carcinogenicity to humans-tested
• Category 3B Not classifiable as to carcinogenicity to humans-untested
• Category 4 Probably not carcinogenic to humans [7]

Mutagens: Substances capable of impairing or modifying genes.

• Category 1 Known to be mutagenic to humans
• Category 2 Should be regarded as if they are mutagenic to humans
• Category 3 Cause possible mutagenic concern for humans

Teratogens: Substances toxic to reproduction (developmental toxicity or impairment of fertility).

• Category 1 Known to be toxic to reproduction in humans
• Category 2 Should be regarded as if they are toxic to reproduction in humans
• Category 3A Cause possible developmental toxicity for humans
• Category 3B Cause possible impairment of fertility for humans

Sensitisers: Are divided into two categories:

i)      a respiratory sensitiser is a substance that will induce hypersensitivity of the airways following inhalation of the substance.

ii)     a contact sensitiser is a substance that will induce an allergic response following skin contact.

The EU only ascribes one category to skin sensitisers but the US OSHA [8] divides Category 1 sensitisers into 2 sub-categories as follows:

Respiratory Sensitiser Categories:

• Category 1A: Substances showing a high frequency of occurrence in humans; or a probability of occurrence of a high sensitization rate or severity of reaction in humans (May cause allergic or asthmatic symptoms or breathing difficulties if inhaled [Respiratory Sensitiser EU])
• Category 1B: Substances showing a low to moderate frequency of occurrence in humans; or a probability of occurrence of a low to moderate sensitization or severity of reaction (May cause allergic or asthmatic symptoms or breathing difficulties if inhaled [Respiratory Sensitiser EU])

Contact Skin Sensitiser Categories:

• Category 1A: Skin Sensitiser - May cause allergic skin reaction (≥ 0.1%)
• Category 1B: Skin Sensitiser - May cause allergic skin reaction (≥ 1.0%)

The US based OSHA organisation also has some additional skin and eye related categories: [9]

Skin Corrosion

• Category 1A: serious irreversible effects on skin (≤ 3 min, observed ≤ 1hour)
• Category 1B: serious irreversible effects on skin (> 3 min ≤ 1 hour, observed ≤ 14 days)
• Category 1C: serious irreversible effects on skin (> 1 hour ≤ 4 hours observed ≤ 14 days)

Skin Irritant:

• Category 2:  reversible irritations to skin

Eye Corrosiveness

• Category 1: serious irreversible effects to eyes
• Category 2A: irritating to eyes
• Category 2B: mildly irritating to eyes

Endocrine disruptors:

A whole variety of chemicals in common use today disrupt human and animal hormones. Some do this by mimicking the hormone oestrogen. They can cause developmental defects such as sperm loss, breast tissue growth in males, sex conversion in animals and recently they have begun to be linked to breast cancer. Such chemicals typically are used as plasticisers e.g. DOP and other phthalates in vinyls (now banned in children's toys) and other chemicals such as BPA found in polycarbonates and epoxies. The EU defines endocrine disruptors as follows:

• Category 1: evidence of endocrine disrupting activity in at least one species using intact animals;
• Category 2: at least some laboratory evidence of biological activity related to endocrine disruption;
• Category 3: no evidence of endocrine disrupting activity or no data available [10]

Within ESCAP, categories where 'No data is available' trigger closer inspection and more detailed research and the 'precautionary principle ' is carefully considered in the risk assessment stage (see below for more information).

Ecological Health issues

Substances with the classifications listed above are obviously all still relevant in ecosystem health. However, in water based ecosystems, other criteria also become relevant.

Eutrophication

This is the process by which a body of water acquires a high concentration of nutrients, especially phosphates and nitrates. These typically promote the excessive growth of algae. As the algae die and decompose, high levels of organic matter and the decomposing organisms deplete the water of available oxygen, causing the death of other organisms, such as fish. Eutrophication is a natural, slow-aging process for a water body, but human activity can greatly speed up and intensify this process. [11]

 

Figure: Example of algal blooms from eutrophication [12]

Acidification

Acidification occurs in air when compounds like sulphur or nitrogen (and their oxides or ammonia) are emitted, typically from fossil fuel energy generation or from industrial, petrochemical and vehicular pollution.

Acidification typically occurs in soils when acid rain falls, or through the overuse of synthetic nitrogen fertilisers, or due to poor land management practices.

In lakes and streams, it can occur from direct deposition of pollutants into lakes and streams or, more commonly, through runoff and soil erosion from the surrounding areas.

It can also occur in oceans when increased levels of carbon dioxide (from human or natural processes) dissolve in the surface waters of the ocean, forming a solution of carbonic acid. Increasing an ocean's acidity reduces the ability of organisms to calcify their shells.

Figure: Example of trees killed by acid rain [13]

How to determine if a substance or mixture is harmful

To determine whether a substance or mixture is hazardous, using the HSIS, we must follow this approach:

Step 1: Identify each ingredient using the substance name, CAS Number or UN number

Step 2: Determine if the concentration of any ingredient is above the minimum concentration cut-off level (if so, the mixture is determined to be hazardous).

If any ingredient in the mixture does not appear on the HSIS, or is listed without at least one concentration cut-off level, then we must check other databases such as ESIS or GHS. If a mixture contains more than one ingredient that is in the HSIS consolidated listing, and all ingredient concentrations are below their respective minimum concentration cut-off levels, the mixture may still be considered hazardous if one or more of these ingredients exhibit corrosive, irritant or acute lethal effects.

The Precautionary Principle

The precautionary principle or precautionary approach states that if an action or policy has a suspected risk of causing harm to the public or to the environment, in the absence of scientific consensus that the action or policy is harmful, the burden of proof that it is not harmful falls on those taking the action.

This principle allows policy (and Standard) makers to make discretionary decisions in situations where there is the possibility of harm from taking a particular course or making a certain decision when extensive scientific knowledge on the matter is lacking. The principle implies that there is a social responsibility to protect the public from exposure to harm, when scientific investigation has found a plausible risk. These protections can be relaxed only if further scientific findings emerge that provide sound evidence that no harm will result.

In some legal systems, as in the law of the European Union, the application of the precautionary principle has been made a statutory requirement. [14]

How the ecolabels deal with chemical impacts

Global GreenTag^CertTM

The Global GreenTag^CertTM Standard does not allow the use of its label if a product contains certain very toxic and persistent chemicals or categories of chemicals. A broader group is not accepted beyond a 0.1% threshold limit, subject to risk assessment. Global GreenTag^CertTM then divides all remaining chemicals into categories by R-Phrase and assesses and scores them by threshold and a range of exposure limits and risk evaluation. There are then specific supplementary standards where the cut-off levels vary with the application, with the more critical applications reducing the threshold values even further to 0.001%. Passing the toxicity criteria is mandatory if the product is to be allowed to carry the label.

Furntech Green Tick

The Furntech Green Tick Standard does not allow the use of its label if a product contains some specific chemicals and categories of chemicals such as very toxic chemicals and APEOs, heavy metals to NAOELs and carcinogens to 0.1%. A chemical management plan is used that identifies toxic chemicals and ensures safe handling procedures. The range of R-Phrases assessed is less broad than either GECA or GreenTag. Passing the toxicity criteria is mandatory, if a product is to be allowed to carry the label.

Carpet Institute ECS

The ECS scheme does not allow the use of its label if a product contains very toxic compounds, Group 1 and 2A carcinogenic, mutagenic and teratogenic compounds. It also restricts the use of its label if 378 specific chemicals on the REACH 'SIN' list to a 0.1% threshold value. It requires the presence of heavy metals to comply with NOAEL levels and free monomer residues to 10mg/kg of polymer weight (0.001%). Passing the toxicity criteria is mandatory if a product is to carry the label, except for level 1 which only assesses VOCs and does not look at any toxicity requirements for raw materials.

SMaRT

Use of the SMaRT Standards label is only allowed if Stockholm Convention Persistent Organic Pollutants are not present at more than 0.1% in the product. Likewise, carcinogens, VOCs and several other specific chemicals cannot be present in products if they are to be labelled with a SMaRT label. Credits are given for inventorying over 1200 listed chemicals and achieving voluntary reductions. No specific minimum threshold values for these chemicals are required, before a SMaRT label is allowed to be used.

GECA

Depending on the standard used, GECA labels cannot be used if the product contains certain very toxic and persistent chemicals or categories of chemicals. GECA selects a limited range of specific R-Phrases and uses 0.1% cut-off levels for a pass/fail assessment. The cut-off levels vary with the application, with more critical applications reducing the threshold values. Passing the toxicity criteria is mandatory if the product is to be allowed to carry the label.

Ecospecifier Verified

Similar to Global GreenTag^CertTM the Ecospecifier Verified Products Standard label cannot be used on products containing certain very toxic and persistent chemicals and categories of chemicals. Likewise, labelling is not allowed if a broader group of chemicals is present beyond a 0.1% threshold limit, subject to risk assessment. It then divides all remaining chemicals into categories by R-Phrase and assesses and scores them by threshold and a range of exposure limits and risk evaluation. There are then specific supplementary standards where the cut-off levels vary with the application, with the more critical applications reducing the threshold values even further to 0.001%. Passing the toxicity criteria is mandatory if the product is to be allowed to carry the label. All toxicity and environmental claims are assessed in accordance with ISO 14021.

 

References

All last accessed on 1/8/12.