COSHH Essentials

COSHH Essentials is a tool developed by the UK Health and Safety Executive. It’s a “control banding” technique which was originally intended to help small companies, without access to expert help, determine what controls are needed to control exposure to the hazardous substances they use or handle.

It was originally published as a “hard copy” manual in 1999, an online version appearing a few years later. The hard copy is no longer available.

In essence COSHH Essentials is a mathematical modelling tool which estimates exposure. The user enters some basic information on the substance being used (“R phrases”, boiling point or “dustiness”  and the amount used). The tool uses these details to determine which “control approach” is appropriate and the user is directed to simple control sheets relevant to the risk and the type of process.

It is a very simple tool that can work in straightforward situations where a single substance or “preparation” is being handled. However, it has some very serious limitations.

The following slides provide a more detailed outline of the process and a couple of examples to show how it works in practice

The two examples used in the presentation illustrate some of the strengths and weaknesses of the approach.

In the first scenario, where a low hazard powder is being weighed and mixed with water to form a slurry the only significant risk is inhalation of airborne dust and the tool works quite well. The specified control – local exhaust ventilation – seems appropriate. The scenario is based on a real situation where I recommended installing an extracted booth, and one of the control sheets generated by the tool provides a suitable design.

However, I think the conclusions and guidance provided for the second example – cleaning rollers with solvent – illustrate some of the problems with COSHH Essentials. Here there are two significant risks – inhalation of solvent vapours and skin contact with the liquid solvent. The tool is particularly poor where the latter is an issue. It doesn’t attempt to assess skin exposure other than directing the user to personal protective equipment (PPE) wherever skin or eye hazards are flagged up by the R phrases. Use of PPE should always be the last resort. Preventative measures and engineering controls are always preferable and should be considered first. This applies to skin contact as well as inhalation risks. In fact, protective gloves are rarely as effective as the user perceives and their introduction can sometimes be counter productive due to this. So, for this scenario I would have looked at finding an alternative solution such as using an applicator that minimised contact. Gloves might still be needed, but as a backup rather than the primary control.

My second concern with the output from the model for the second scenario is that it recommends enclosure of the process. Personally, I think this is over cautious. I think that local exhaust ventilation (LEV) would be adequate here. Enclosure would require automation and also LEV and, although quite feasible, this approach would be relatively expensive and I wouldn’t consider it to be “reasonably practicable” where only a few litres of solvent are used per day. This problem occurs because the usage category “medium” is specified where litre quantities of a substance are used. There is likely to be a big difference in risk between using 4 or 5 litres of a substance and 500 litres – yet in both cases the user is directed to classifying the quantity used as “medium”. I think the category is too broad. With this particular scenario, it would be better to consider the quantity as “small”. The tool would then specify “engineering controls” – effectively LEV – as the appropriate control approach. This seems much more reasonable to me. However I think that a user is most likely to classify use as “medium”. In this case COSHH Essentials is over cautious. That’s better than underestimating the risk, but could lead to more expense than really necessary.

In both the scenarios only a single substance was being used for relatively short durations. Where highly toxic substances, such as carcinogens, are used, or the process is more complex, particularly where there is more than one material or where substances are generated during the process, the use of COSHH essentials is unlikely to be appropriate.

Lead exposure during soldering


“Soft soldering” is a widely used technique in the electronics industry for joining electronic components to printed circuit boards. Traditionally the solder was an alloy of lead and tin, typically containing about 40% lead.  It is well known that lead is a highly toxic metal, potentially causing a wide range of harmful effects. Children are particularly susceptible.

The use of lead solders has been effectively banned in Europe for most purposes since 1 July 2006 by the EU Directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment (2002/95/EC), commonly referred to as the Restriction of Hazardous Substances Directive or RoHS. The reason for this change was to reduce the discharge of lead into the environment, particularly during the disposal of electronic components. However there are still some applications where lead based solders are permitted.

Where lead containing solders are used, the risk from lead is usually very low. This may seem strange given the high percentage of the metal in the solder. However, soldering is usually carried out at a temperature of around 380 C and significant lead fume is only evolved at temperatures above 450 C. So exposure by inhalation is normally insignificant. This is recognised in the Approved Code of Practice (ACoP) supporting the Control of Lead at Work Regulations 2002 (CLAW). Table 2 in the ACoP (reproduced below) lists processes which are not liable to result in significant exposure to lead. This list includes “Low-temperature melting of lead (below 500°C)” during soldering.


Soldering can produce “dross” – fine particles of solder. Inhalation  is likely to occur occur if the dust is disturbed and it may be accidentally ingested if the fingers and hands become contaminated. So its important that appropriate precautions are taken to minimise these risks. However, with well managed soldering processes lead exposure should be minimal.

Despite this a client of ours who carry out soldering with lead based solders (they undertake a process which is exempt from the restrictions imposed by the Restriction of Hazardous Substances Directive) had a visit from a Factory Inspector who insisted that they carry out air sampling and blood lead measurements. The management, who are very conscientious about their responsibilities regarding health and safety, pointed out the guidance in the ACoP, but despite this the Inspector was insistent.

The company asked us to undertake the sampling.  I’m glad to say that, as expected, exposures were very low. In fact no lead was detected on any of the samples, meaning that the time weighted average concentrations were less than 2% of the lead exposure limit.

It’s disappointing that the Factory Inspector asked the company to pursue this issue, which involved a significant cost, especially as the HSE’s own guidance is quite clear. Perhaps this case suggests that general Inspectors need to be given more training on occupational hygiene.

The real issue with soldering is the fume produced by the flux – usually  containing colophony (also known as rosin), which is manufactured from pine resin, and is usually contained within the soldering wire (rosin cored solder), although liquid fluxes are also used in some cases.   The flux is needed to prevent oxidation of components, remove contaminants from the surface of the components, and reduce the surface tension of the molten solder. When heated during soldering it vapourises and condenses into fine particles, which form the fume which is usually clearly visible as a white smoke. Thermal degradation of the colophony also generates irritant gases.


Rosin cored solder fume is a well established respiratory sensitiser, and is one of the main causes of occupational asthma in Great Britain. Colophony fume is generated at temperatures above about 180 C, well below the temperatures associated with soft soldering. So significant concentrations can be evolved. The higher the temperature, the more fume is generated.  The lead free solders introduced since the Restriction of Hazardous Substances Directive was implemented in 2006 tend to have higher melting points than the traditional lead:tin types. So, ironically, the elimination of lead for environmental reasons has led to a potential for increased exposures to a potent asthmagen in the workplace.

(Note: HSE have produced guidance on the hazards and legal requirements and on the control of rosin cored solder fume.)

Skin Exposure and COSHH Assessments


Recently I’ve been working with a client on a review of their COSHH assessment protocol. Many of their processes involve the handling of lubricants, sealants and adhesives which have a low volatility and present only a minimal risk from inhalation. The main risk of exposure is from skin contact. However we found that their COSHH assessment procedure mainly focuses on inhalation and so, consequently, many of their assessments haven’t properly considered skin contact.

In my experience this is quite often the case. COSHH assessments tend to focus on inhalation exposures. Skin exposures are commonly neglected. Where they are considered controls are usually poor – in most cases personal protection being used.

Skin exposure can lead to two main concerns

  • direct effects on the skin (e.g. irritation, skin burns, skin sensitisation)
  • absorption through the skin, contributing to overall body burden.

Even the HSE’s basic risk assessment tool, COSHH Essentials, doesn’t properly consider these risks. Skin hazards are identified if the substances have been assigned the appropriate R phrase for skin effects, but skin absorption is not considered. Even where skin effects are identified, the output from COSHH Essentials will recommend the use of PPE, which should really be the last resort, not the only solution suggested.

According to the HSE

  • In 2009/10, an estimated 22,000 individuals reported experiencing “skin problems” which they believed to be work-related, according to the Labour Force Survey.
  • There were 2,455 cases of occupational skin disease in 2009 reported by dermatologists and occupational physicians reporting in the THOR (EPIDERM and OPRA) network.

In the USA OSHA reports that in 2006, 41,400 recordable skin diseases were reported by the Bureau of Labor Statistics (BLS) at a rate of 4.5 injuries per 10,000 employees, compared to 17,700 respiratory illnesses with a rate of 1.9 illnesses per 10,000 employees.

So direct effects on the skin is clearly a significant problem in industry (and these statistics probably underestimate the extent of skin problems).

It is much more difficult to determine the extent of problems due to skin absorption. Many industrial organic solvents and some other less common substances can be absorbed through the skin. It’s not always easy to identify them. EH40, HSE’s list of Workplace Exposure Limits and the ACGIH Threshold Limit Values include “SK notations” which are applied to substances where skin absorption can make a substantial contribution to body burden. In addition,not all substances in EH40 and the TLV list than can pass through intact skin have been assigned Sk notations, and WELs and TLVs have only been applied to a small proportion of substances encountered in the workplace. However, there is a good chance that any solvent that can affect the skin can also be absorbed.

So skin contact is something that needs to be properly considered during COSHH assessments. Evaluating the degree of risk isn’t easy – particularly with skin absorption where there isn’t a good universal method available for quantifying absorption. However, COSHH is about controlling risks – the  assessment is not an end in itself but the means of deciding which risks need to be controlled. So  where skin contact occurs the best approach is to identify suitable controls.

Unfortunately, in my experience, the usual response by employers is to issue personal protection such as gloves or protective clothing. (And, the HSE’s own  COSHH Essentials takes this approach). PPE should only be used as a last resort. The COSHH Regulations themselves  specify that it should only be used “where adequate control of exposure cannot be achieved by other means”. This doesn’t only apply to respiratory protection.

Where chemical protective gloves and clothing are used, they rarely provide effective protection other for short duration tasks. Yet employers and workers often have a misguided belief in their effectiveness which can actually increase the risk to health. The best approach is to look to change the working method so that skin contact doesn’t occur, or is a least minimised to the lowest level practicable, or to find a suitable engineering control. Appropriate gloves can then be worn as a secondary control.


Picture credits:

HSE Work-related skin disease image library

Preventing dermatitis at work. Advice for employers and employees

Diesel exhaust emissions – what to measure?

fork truck

We recently had a query from a client who’d had a visit from their local Factory Inspector. The client has a large warehouse where they operate diesel powered fork lift trucks. The Inspector asked about the client about their risk assessment of the emissions and then suggested that they arrange to measure the emissions.

Diesel exhaust emissions are a complex mixture of gases and particulate matter. Major components include :

  • carbon;
  • nitrogen;
  • water;
  • carbon monoxide;
  • aldehydes;
  • nitrogen dioxide;
  • sulphur dioxide;
  • polycyclic aromatic hydrocarbons (PAHs).

Quite a number of these contaminants are irritant gases, that can affect the eyes and respiratory system. There are also concerns about the potential risk of cancer from inhaling this complex mixture. Some studies have shown a small increase in lung cancer for people exposed to diesel exhaust emissions and the International Agency for Research into Cancer (IARC) have concluded that diesel engine exhaust is probably carcinogenic to humans. This may be due to the presence of PAHs in the emissions.  Another consideration is that, due to the way it is formed, the particlulate matter is nano-sized, and can be absorbed through the lungs and transported around the body. There are concerns that nano-particles may cause adverse effects on the heart and cardiovascular system

Although a number of the individual components have Workplace Exposure Limits (WELs), and can be measured fairly easily, simply quantifying each substance does not give an adequate evaluation of the risk, particularly as there could be additive or more complex interactions. In any case, some of the components presenting the greatest concerns (nano-particles, PAHs) do not have WELs.

So although some components can be measured, it’s not so easy to interpret the results.  In such cases it is best to remember the real objective of risk assessments – i.e. to determine what controls are required. The HSE have published some guidance in their publication Control of diesel engine exhaust emissions in the workplace (HSG187). It is usually obvious when there is a significant problem with the emissions from diesel engines. If visible black smoke is pouring out of the exhaust pipe something needs to be done! It’s not always so obvious, but the UK Health and Safety Executive (HSE) have developed some guidelines based on observations, subjective assessment of irritancy and measurement of carbon dioxide levels, which give an indication of whether control is adequate.

Table 1 – Guidelines for the assessment of the level of exposure to DEEEs – From HSG 187


Carbon dioxide can be measured easily using a simple colorimetric indicator tube. But note that in this instance it isn’t appropriate to compare the results with the WEL for the gas – it is being used as an “marker” of the overall emissions and standard of control.

It’s quite possible to measure the particulates, but the analysis is very expensive and there isn’t a WEL. Without a standard against which the results can be compared, measurement results don’t help us to decide on the degree of risk and whether improved controls are needed. In this case, particulate sampling is an expensive exercise which doesn’t help us to draw useful conclusions. Using a pragmatic approach of observations and simple measurements of marker compounds is the most cost effective way of assessing the risk and deciding on what controls are needed.

The following provide some further information on the assessment and control of diesel engine exhaust emissions:

Health and Safety Executive – indg286 Diesel Engine Exhaust Emissions

Health and Safety Executive Control of diesel engine exhaust emissions in the workplace (HSG187)

Rogers and Davies Diesel Particulates—Recent Progress on an Old Issue The Annals of Occupational Hygiene 2005 Volume49, Issue6 Pp. 453-456

Diesel Engine Exhaust – California Department of Health Services

Photo credit: Stock:xchng

Are the Tate’s sunflower seeds a risk to health?

sunflower seeds 1

Last week I took a short break in London. On Monday we visited the Tate Modern to see the Gauguin exhibition that had recently opened. On arriving at the gallery we noticed that there was something going on in the Turbine hall. We could see that the floor in a large area of the hall was covered with what appeared to be gravel. There were a few people standing and walking on it with some of them taking photos. However, we weren’t allowed access – the area was cordoned off. There were also a number of people on the mezzanine floor wandering around with folders under their arms. I asked one of the gallery attendants what was going on and was told that the “gravel” was a newly installed work by the Chinese artist Ai Weiwei, consisting of 100 million individually handmade ceramic sunflower seeds. According to the Tate press release

Each ceramic seed was moulded, fired at 1300°C, hand-painted and then fired again at 800°C.”

For the first couple of days visitors were allowed to interact with the work – walking  and standing on the “seeds” (we hadn’t been allowed access as it was the press showing when we visited). However, on Friday the gallery announced that  this would no longer be allowed as they had

…  been advised that the interaction of visitors with the sculpture can cause dust which could be damaging to health following repeated inhalation over a long period of time. In consequence, Tate, in consultation with the artist, has decided not to allow members of the public to walk across the sculpture. “

No details have been provided on the risk assessment that led to this decision, but it appears that the seeds can be crushed underfoot generating dust that could become airborne and then inhaled. What could this dust consist of?

Although no exact details are available on the composition of the seeds, porcelain is made from a number of materials that contain crystalline silica. Respirable particles of this common mineral can cause “silicosis” – a serious, debilitating lung disease, where scar tissue is deposited in the lungs reducing their ability to transfer oxygen into the blood and leading to other complications such as emphysema. For the condition to develop exposure has to occur over a long period of time. A single, brief exposure won’t lead to any harmful effects.

A quick search of the literature throws up quite a lot of information on the risk of silicosis during porcelain manufacture, when workers would be exposed to the raw materials, but there does not appear to be much on the hazards presented by inhalation of dust from fired porcelain. Some free crystalline silica is likely to be present, but only as one constituent, and it’s unlikely that all of this will be respirable.

So some of the dust generated by people walking over the seeds may be hazardous, but what really matters is the risk to health. This is determined not only by the hazard, but also the  exposure to the dust, which depends on the concentration and the duration and frequency of exposure.

Risk = hazard x level of exposure x duration x frequency

Even if all the dust did consist of respirable crystalline silica,  I think that it is unlikely that the risk to visitors would be significant. Its difficult to estimate what the dust concentration would be, but as the Tate themselves state, the dust “could be damaging to health following repeated inhalation over a long period of time”. Most visitors from outside London are probably only likely to visit the exhibition once and would perhaps spend a couple of hours in the Turbine Hall. Even if the concentration of crystalline silica was above the Workplace Exposure Limit (which is probably unlikely) their exposure would not constitute “repeated inhalation over a long period of time”.

Perhaps the concerns are for the health of the staff who work in the gallery (although that is not what the Tate are saying). They clearly would have a longer and more frequent exposure to the dust. The risk then, would depend on the concentration of the dust in the Turbine Hall. I don’t know whether the Tate have properly assessed this, but it would be relatively easy to monitor the dust levels to allow an informed judgement to be made of the risk.

It is possible that there are other components of concern in the dust. The seeds are all painted and paint pigments can contain toxic materials. I would have hoped that the artist would have avoided using such paints due to the potential risks to the artisans who created the seeds for him. However, even if the pigments did include toxic components the same considerations would probably apply as for the respirable crystalline silica – i.e. the risk would be from repeated exposure to a significant concentration over a long period of time and, as with the silica, it is unlikely that this would be the case, certainly for visitors.

It seems likely that the Tate have overreacted somewhat. I think the health risk to visitors due to exposure to any dust will be negligible. So this could be a case of “health and safety gone mad” or perhaps the Tate have other reasons for forbidding visitors from walking on the work.

Photo credit : arkadin55

Further information on silica hazards and control of risks are available from


UK Health and Safety Executive


What’s a “confined space”?

I recently received the following query regarding the application of the Confined Space Regulations 1997:

“is the intent that any room that has a hazard in it is considered a Confined Space?  Let’s say we have a room with 2 doors, some general dilution and exhaust ventilation, and has a CO2 line running through it with several flanged connections.  The line has never leaked, but I suppose it could if something breaks.  Is that a confined space according to the regs?”

The term “confined space” has a particular legal meaning. Once a space is defined as such then the requirements of the “Confined Spaces Regulations 1997” become applicable and employers are required to

  • avoid work in the confined space “as far as reasonably practicable”
  • where work is necessary, ensure that there is a safe system of work
  • make arrangements to safely rescue anyone who becomes incapacitated within the confined space.

It isn’t true that any room containing a hazard would be considered as a “confined space”. However, I would probably categorise the situation described in the query as such.  I once had to deal with a similar situation – a pub cellar where there are CO2 cylinders. There was a risk of a cylinder “bursting” which could release gas into the room. HSE does include “unventilated or poorly ventilated rooms” as an example of a confined space in their guidance on the Regulations in their guidance leaflet, indg258 .

Our British approach is a little woolly, but allows flexibility.  The crucial questions to answer when deciding on whether something is a “confined space” are

  1. Is the room “substantially” enclosed? i.e. is access / egress limited?
  2. Is a potential hazard present in the room ( or one is “reasonably foreseeable”)?
  3. In the case of a hazardous gas/vapour/fume/dust, is ventilation limited so that a dangerous concentration is possible?

If the answer to each of these is “yes”, particularly if access/egress limited, then I’d classify it as a confined space and the Confined Spaces Regulations would apply.

In the example given in the query, it appears that there is limited access/egress and there is a reasonably foreseeable risk (albeit small) of a leak. If the concentration could build up to a dangerous level than I’d  definitely classify it as a confined space under the Regulations. So the crucial test is whether a leak would lead to a dangerous concentration.

Detailed guidance on the Regulations are available here