This is an interim WES or BEI
Microgram. It is a unit of mass equal to 1 millionth of a gram or 1 thousandth of a milligram.
Micrometre, or ‘micron’. Its size is 1 millionth of a metre.
Micromole, a unit of measurement for the amount of substance, or chemical amount.
The American Conference of Governmental Industrial Hygienists (ACGIH®) is a 501(c) (3) charitable scientific organisation, established in 1938, that advances occupational and environmental health. Examples of this include their annual edition of the TLVs® and BEIs® book and Guide to Occupational Exposure Values.
A mass or cluster.
Airborne contaminants
Potentially toxic dusts, fibres, fumes, mists, vapours, or gases contaminating the air.
A term applied to a substance that can cause an allergic response (development of an allergy to it, with allergic symptoms on re-exposure).
Allergic sensitisation
The more often the worker is exposed to an allergen, the more severe the worker’s reaction to the allergen becomes. Even at low exposures to the allergen, a sensitivity reaction may occur.
Animal studies
Also known as ‘Animal testing’: the practice of using animals in experiments, including for biomedical research or toxicology testing.
Background level
Level of a substance in a worker’s biological sample that can occur naturally (without any workplace exposure). The background level can be due to the substance’s normal presence in the environment or diet, or produced in the body itself.
Exposure can also be estimated by biological monitoring.
Biological agent reference value (BRV)
Based on the 95th percentile in the general New Zealand population.
Biological assay
Also known as Bioassay, it is a particular type of test or experiment designed to determine the presence and/or concentration of a substance.
Biological exposure index (BEI)
Guidance values for assessing biological monitoring results. It indicates a concentration below which nearly all workers should not experience adverse health effects from exposure to a particular substance.
Carboxyhaemoglobin level
A good indicator of the level of carbon monoxide present in the bloodstream. It is formed when haemoglobin binds preferentially to carbon monoxide instead of oxygen, which can severely reduce the delivery of oxygen to various parts of the body.
carcinogen category 1
Known or presumed human carcinogen.
carcinogen category 2
Suspected human carcinogen.
The description given to those hazardous/toxic substances that can cause cancer or contribute to its development.
Short for Chemical Abstract Services Registry Number. This Registry assigns a unique identifying series of numbers to each individual chemical.
Causal relationship
The relationship between an event and another event, where the second event is a consequence of the first. For example, exposure to a confirmed cancer-causing agent may, depending on the extent of the exposure, lead to cancer in the exposed person.
Ceiling (WES-Ceiling)
A concentration that should not be exceeded at any time during any part of the working day.
Decilitre. Its volume is one tenth of a litre or 100 millilitres.
Dermal sensitiser.
Discrete solid particles suspended in air. See section on ‘Aerosols’ in ‘Applying workplace exposure standards’ for a more detailed definition.
Elimination rate
The calculated (or estimated) rate at which a substance is eliminated from the body.
Epidemiological studies
Studies (of various types) on human populations, which are designed to help identify specific causes of adverse health effects, and the relative contribution of different causes.
Equivalent aerodynamic diameter (EAD)
The diameter of a sphere of ‘unit density’ (1 gram per cm³) that exhibits the same aerodynamic behaviour as that of the particle (of any shape or density) being measured.
Excursion limit (EL)
For many substances with a WES-TWA, there is no WES-STEL. Nevertheless, excursions above the WES-TWA should be controlled, even where the 8-hour WES-TWA is within the recommended limits. Excursion limits apply to those WES-TWAs that do not have WES-STELs.

Transient increases in workers’ exposure levels may exceed three times the value of the WES-TWA level for no more than 15 minutes at a time, on no more than four occasions spaced one hour apart during a workday, and under no circumstances should they exceed five times the value of the WES-TWA level. In addition, the 8-hour TWA is not to be exceeded for an 8-hour work period.
Fibres not less than 5μm and not more than 100μm in length, less than 3μm in width, and with a length to width ratio of no less than 3:1.
A substance that is known to generate ‘fibrotic’ reactions in body organs or tissue. This process is also known as fibrosis, which is the development of excessive fibre-like or fibrous tissue, similar to scarring.
Very small airborne solid particulates with diameters generally less than 1m. They may be formed by thermal mechanisms (for example, condensation of volatilised solids, or incomplete combustion) or chemical processes (for example, vapour phase reactions). Agglomeration of fume particles may occur, resulting in the formation of much larger particles.
A state of matter characterised by low density and viscosity (compared to liquids and solids), and can usually expand and contract with changes in pressure and temperature. Gases can be in the form of individual atoms of an element (for example, argon) but more usually comprise molecules, containing more than one atom of one or more elements (for example, carbon dioxide).
GRWM Regulations
Health and Safety at Work (General Risk and Workplace Management) Regulations 2016.
Hazardous substance
A substance (in gas, liquid, or solid form) that has one, or more, of the following properties:
• explosive
• flammable
• oxidising
• toxic (harmful to humans)
• corrosive
• ecotoxic (harmful to animals, soil, water, or air).
The Hazardous Substances and New Organisms Act 1996.
Health and Safety at Work Act 2015.
The Inhalable Fraction and Vapour (ifv) notation is used when a material exerts sufficient vapour pressure such that it may be present in both particle and vapour phases, with each contributing to a significant portion of exposure.
The property of a living (biological) organism that is capable of causing an infection. This can occur when the body is invaded by pathogenic (disease-causing) microorganisms.
Inhalable dust
Portion of airborne dust that is taken in through the mouth and nose during breathing.
A substance capable of causing tissue inflammation when it contacts the skin, eyes, nose, or respiratory system (usually with associated subjective feelings of irritation and discomfort, as well as objective evidence of inflammation).
Latency period
The period between contact with a chemical substance or biological pathogen and the development of symptoms.
A term used to describe the process by which a substance is changed or ‘broken down’ in the body, into metabolites (changed substances). These metabolites are usually easier for the body to eliminate than the original substance is, but sometimes can be more toxic.

‘Metabolism’ is also used more generally to describe the numerous, wide-ranging set of chemical reactions required for the body to function normally.
mg = milligrams, and m³ = cubic metres. mg/m³ is used for reporting the concentration of solids (like dusts or metal fume) in the worker’s atmosphere (as mass per volume of air).

It can also be used for reporting airborne concentrations of liquid particles (mists) or even gases, although gases are usually reported in ppm.
Small droplets of liquid suspended in air. See section on ‘Aerosols’ in ‘Applying workplace exposure standards’ for a more detailed definition.
Sampled by a method that does not collect vapour.
Polychlorinated Biphenyls (PCBs) are Persistent Organic Pollutants (POPs), which will be phased out in New Zealand by 2016. They are banned from importation, production, and use. Exemptions allow for the storage of PCBs for a limited time and for small-scale research/laboratory use.
Pharmacokinetics (or toxicokinetics)
Pharmacokinetics describes the movement of a substance through the body. It includes the processes of absorption, distribution, modification, and elimination of the substance.
A vertically elongated tube that lies behind the nose, mouth, and larynx. The middle section, the oropharynx, is located behind the throat. It serves as the upper passageway for the digestive and respiratory tracts, transporting air, water, and food as necessary.
Parts of vapour or gas per million parts of air.
The value for respirable dust.
Respirable dust
The fraction of total inhalable dust that is able to penetrate and deposit in the lower bronchioles and alveolar region of the lungs.
Respiratory system
The complex of organs and structures that performs breathing or respiration. Normally this results in adequate ventilation, where sufficient amounts of ambient air are transported into the terminal regions of the lung, where the exchange of oxygen for carbon dioxide produced by the body occurs. (The oxygen is circulated through the body and the carbon dioxide is exhaled.)

The main organs and structures involved in the respiratory system are:
• nose
• pharynx
• larynx
• trachea, bronchi, and lungs
• pleura (membrane surrounding lungs)
• blood and nerve supply.
Respiratory sensitiser.
Rubber fume
Any fume that evolves during the blending, milling, and curing of natural rubbers or synthetic elastomers.
Rubber process dust
Dust generated during the manufacture of goods using natural rubber or synthetic elastomers.
Simple asphyxiant.
Safety data sheet
A document that describes the hazardous properties of a substance, that is, its identity, chemical and physical properties, health hazard information, precautions for use, and safe handling information.
Simple asphyxiant – may present an explosion hazard.
The Scientific Committee on Exposure Limit Values (SCOEL) is a committee of the European Commission established in 1995 to advise on occupational exposure limits for chemicals in the workplace within the framework of Directives 98/24/EC and 90/394/EEC.
Short-term exposure limit (WES-STEL)
The 15-minute time weighted average exposure standard. Applies to any 15-minute period in the working day and is designed to protect the worker against adverse effects of irritation, chronic or irreversible tissue change, or narcosis that may increase the likelihood of accidents.

The WES-STEL is not an alternative to the WES-TWA; both the short-term and time-weighted average exposures apply. Exposures at concentrations between the WES-TWA and the WES-STEL should be less than 15 minutes, should occur no more than four times per day, and there should be at least 60 minutes between successive exposures in this range.
Skin absorption.
A substance identified in this document that has properties making it toxic to human health.
Synergistic effect
This occurs when the combined effect of two chemicals is substantially greater than the sum of the effects of each chemical on their own (for example, 2 + 4 = 20 (not 6, which would be a simple additive effect)).
Terminal velocity
Terminal velocity occurs when the downward force of an object is equalled by the upward force of the object’s drag, making the net force on the object zero. In this state, the velocity (speed) of the object remains constant.
Time-weighted average (WES-TWA)
The average airborne concentration of a substance calculated over an eight-hour working day.
Unciliated airways
In the upper respiratory tract, fine hair-like projections from cells (cilia) ‘sweep’ in unison to remove or clear fluids and particles. In the unciliated airways of the lower respiratory tract (the alveolar region), there are no cilia.
A vapour is the gaseous form of a substance which at normal temperature and pressure exists predominantly as a liquid or solid. This distinguishes it from compounds which exist as gases at room temperature.
A range of airborne contaminants are associated with gas and arc welding. The type of metal being welded, the electrode employed, and the welding process will all influence the composition and amount of fume. Gaseous products such as oxides of nitrogen, carbon monoxide, and ozone may also be produced.

Exposure assessment of welding fume should be based on measurement of known or expected components in welding fume which would include metal constituents as well as shielding gases and contaminants produced during combustion of surface coatings and cleaning products, where present.
Worker’s breathing zone
A hemisphere of 300mm radius extending in front of the worker’s face and measured from the midpoint of an imaginary line joining the ears.
Workplace exposure standard (WES)
Workplace exposure standards are values that refer to the airborne concentration of substances, at which it is believed that nearly all workers can be repeatedly exposed to, day after day, without coming to harm. The values are normally calculated on work schedules of five shifts of eight hours duration over a 40-hour work week.