Health in Construction

A couple of weeks ago I travelled down to Birmngham to give a talk on behalf of the BOHS Breathe Freely initiative at the Health and Wellbeing event at the NEC. The Title of the talk was Managing Health in Construction – What Good Looks Like. An annotated version of the slides I used during the talk are now available on Slideshare

To prepare for the talk I did a little research on the meaures that are readily available to control exposure to contaminants, particularly dust, during common activities on construction sites. A number of studies have been done, both on-site and in the laboratory to assess the effectiveness of water supression and on-tool extraction for power tools. These studies have confirmed just how they can be.

For example

  • A large scale study in Ireland by Healy et al showed that the use of local extraction built into on-tool shrouds could reduce dust exposures by up to 99%
  • Laboratory tests by Thorpe et al showed water suppression on cut-off saws reduced dust levels by up to 99%

Despite this, in a large proportion of cases these engineering controls are not being used with reliance placed on respiratory protection which is often incorrectly used and inadequately managed. So one of the main aims of the BOHS Breathe Freely initiative is to raise awareness of the types of controls that can be used to reduce exposure. Hopefully in the not too distant future we’ll see water supression and on-tool extraction become the norm rather than the exception.

 

References

Measurements of the E€ectiveness of Dust Control on Cut-off€ Saws Used in the Construction Industry. Thorpe et al. Ann Occup Hyg Vol. 43, No. 7, pp. 443-456, 1999

An Evaluation of On-Tool Shrouds for Controlling Respirable Crystalline Silica in Restoration Stone Work.  Healy et al. Ann Occup Hyg 2014;58:1155-1167

Canary Girls

A couple of weeks ago I visited the latest exhibition showing at Manchester City Art Gallery – The Sensory War 1914-2014

This major group exhibition marking the Centenary of the First World War explores how artists have communicated the impact of military conflict on the body, mind, environment and human senses between 1914 and 2014.

Included in the exhibition were a number of pictures illustrating the role of women on the “Home Front”. Due to sending many hundreds of thousands of young men to the trenches in Europe there was a shortage of workers to man the production lines in the munitions factories. The solution was to recruit women.

This lithograph by Archibald Standish Hartrick, who worked as a war artist, shows a young woman filling shells with TNT explosive.

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Women’s Work: On Munitions – Dangerous Work (Packing T.N.T.) c.1917

The “munitionettes” were referred to as the “Canary Girls” as many of them developed yellow skin due to their exposure to the chemicals they were handling.

TNT (2,4,6-Trinitrotoluene) as well as being highly explosive presents a number of serious health effects such as anemia (reduced number of red blood cells and reduced hemoglobin and hematocrit), liver function abnormalities, respiratory complications, and possibly aplastic anaemia (ASTDR).

TNT can interact with haemoglobin to form methaemoglobin, reducing the capacity of the blood to carry oxygen and causing cyanosis – so it’s a chemical asphyxiant. It can also damage the liver, leading to jaundice and the yellow colour of the skin.

Exposure can occur by inhalation of dust and also by skin absorption – both potentially significant for the worker portrayed in the picture. The control measures leave a lot to be desired with what appears to be direct hand contact and only the use of a primitive mask to control inhalation exposure with no evidence of any engineering controls.

For King and Country (1916) by Edward F Skinner Source: Imperial War Museum – used under the terms of the IWM Non Commercial Licence.

Conditions in munitions factories have improved considerably since the First World War and stringent control measures are implemented when TNT is handled. A UK Workplace Exposure Limit of 0.5  mg/m3 (8 hour time weighted average) has been established for 2,4,6-Trinitrotoluene.

One of my colleagues undertook some sampling in a factory where 2,4,6-Trinitrotoluene was being handled recently. I’m glad to say that it was being controlled effectively and the airborne concentration was below the level of detection of the method.

Baker’s asthma

I recently attended the Lane lecture, an annual event hosted by Manchester University’s Centre for Occupational and Environmental Health (COEH), held in honour of Ronald Lane, the first Professor of Occupational Medicine at the University. This year’s lecturer was Professor Paul Cullinan, Professor in Occupational and Environmental Respiratory Disease, National Heart and Lung Institute, Imperial College, London and Honorary Consultant Physician in Respiratory Medicine, Royal Brompton Hospital, London. The title of his talk was “Occupational Asthma: Too much of a bad thing” and was based around two case studies – one about exposure to enzymes in the detergent industry and the second about in-store bakers.  The detergent cases study was reasonably well known but it was interesting to have the overview. It was the second one that I found particularly interesting.

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According to the Health and Safety Executive, exposure to flour dust and additives such as amylase are the second most common cause of occupational asthma in Great Britain. And the numbers of workers affected is increasing.

Apparently 18% of all bread sold in the UK is made in supermarket in-store bakeries. There are 1500 of these "scratch" bakeries in the UK with a total of around 15,000 employees. Having had a number of cases of asthma referred to them from one supermarket,  Professor Paul Cullinan and his colleagues managed to get funding for a study covering 20 supermarkets inside the M25. They found that 15% of the workers employed as bakers were sensitised to either flour dust or amylase (used as a flour improver) or both.

Extensive exposure measurements for flour dust had been undertaken during the study. The geometric mean total dust exposure for bakers was 1.2 mg/m3 (the  paper reporting the findings gives a range two standard deviations either side of the geometric mean of 0.9 to 1.6 mg/m3 ) which means that exposures were well below the current UK Workplace Exposure Limit for flour dust, which is 10 mg/m3 . Given the proportion of the bakers suffering from asthma, this strongly suggests that the limit WEL is far too high.

Although the HSE advise that regular health surveillance is needed for bakers, we were told that of the big 4 supermarkets in the UK, only Sainsbury’s and Morrisons have any health surveillance in place. And there is little evidence that they have implemented measures to control the dust, even though solutions are available that could be applied in supermarket bakeries. Wearing a mask should be the last resort – other measures are possible and preferable – but the supermarkets won’t even allow that as the bakery staff can be seen by customers. 

Bakers asthma in the UK is increasing, and it isn’t surprising given what we were told during the lecture. But the problem could be reduced significantly if well known measures are applied to control dust exposures.

Information on hazardous substances–some useful websites

There is a lot of information on hazardous substances the Internet, but not all of it is properly validated. Finding the information you need just by carrying out a search using a search engine can be frustrating as it can be difficult to sort the wheat from the chaff. However, there are a number of good quality online databases that can be accessed free of charge on the Internet. These are some that I find particularly useful

Toxnet

The US National Library of Medicine’s Toxicology and Environmental Health Information Program (TEHIP) operates TOXNET®, an integrated database system of hazardous chemicals, toxic releases and environmental health.

Particularly useful are

ChemIDplus – A dictionary of over 370,000 chemicals (names, synonyms, and structures) which also includes links to other databases and resources.

Hazardous Substances Data Bank (HSDB) – A databases containing comprehensive, peer-reviewed toxicology data for about 5,000 chemicals.

TOXLINE – A bibliographic database containing references from the toxicology literature. In most cases abstracts are included and they often provide enough information for a practising occupational hygienist.

Other databases on TOXNET® have information on carcinogenicity and mutagenicity test results, genetic toxicology test data and chemicals that can present a developmental and reproductive hazard

ECHA C&L Inventory database

The Classification and Labelling Inventory database, run by the European Chemicals Agency, contains classification and labelling information on notified and registered substances received from manufacturers and importers. It also includes the list of harmonised classifications. The database is refreshed regularly with new and updated notifications.

IFA Databases

The German Institut für Arbeitsschutz der Deutschen Gesetzlichen Unfallversicherung (IFA, Institute for Occupational Safety and Health of the German Social Accident Insurance) has a number of very useful databases. These include

GESTIS – International limit values for chemical agents Occupational exposure limits (OELs)

This database contains occupational exposure limit values for about 1,700 substances, from various EU member states, Australia, Canada (Ontario and Québec), Japan, New Zealand, Singapore, South Korea, Switzerland, and the United States as of March 2012.

It can be viewed online and is also available as app for iPhone, iPodtouch, iPad and Android

GESTIS DNEL Database

A DNEL – or Derived No-Effect Level – are used as part of the REACH risk assessment process and are defined as

“the level of exposure to the substance above which humans should not be exposed”.

The GESTIS DNEL Database provides workplace-related DNELs which have been established by manufacturers and importers under their own responsibility and have been published by the European Chemicals Agency (ECHA)

The database can be viewed online or downloaded as an excel spreadsheet.

GESTIS-database on hazardous substances

A database with information on approximately 8000 substances, including chemical and physical properties, basic toxicological data, advice on handling and first aid information.

Organic compounds – Health hazards

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We’re running the BOHS Module W507, Health effects of hazardous substances, in Chester next week. It’s essentially an introduction to the principles of toxicology together with an overview of the effects of some substances encountered in the workplace.

One group of substances commonly found are volatlile organic compounds (VOCs). They’re used for cleaning applications and as solvents in a wide range of products such as fuels, paints, inks and adhesives. They can be supplied on their own (e.g. trichloroethylene used for vapour degreasing ), or as blends or mixtures (e.g. white spirit, petrol etc.).

The main route of absorption for solvents is via inhalation,  due to their volatility.  But skin exposure is important too. VOCs can affect the skin itself and many can be absorbed through intact skin and absorbed into the bloodstream; with some compounds, this can be a major route of entry into the body.

Environmental legislation has led to a reduction in the amount of VOCs used, but according to the latest statistics from DEFRA, in 2012 there were about a 750,000 tonnes of VOCs emitted to atmosphere in Great Britain.

There are many other less volatile organic compounds used in industry. And some of these, such as diisocyanates, epoxies and organophosphates can have serious impacts of human health.

As one of the new International Modules, the exam for W507 is open book. This means that, unlike the previous equivalent British Module M101, it isn’t necessary to memorise a large volume of facts to pass. In the real world occupational hygienists don’t need to be “walking encyclopaedias” as there are plenty of valid resources that can be used to look up details for less common substances. Although I do think good occupational hygienists will know the effects of the more important “common” substances, particularly the ones they’re likely to encounter in the workplace, such as VOCs.

The following Slideshare presentation provides an introduction to the effects of common organic compounds. You’ll learn more if you attend the course!

Low Toxicity Dusts–Part 2

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In my last post I discussed the evidence that suggests that the “trigger values” of 10 and 4 mg/m3 that are widely used as such by many occupational hygienists for “low toxicity dusts” where an official Workplace Exposure Limit (WEL) hasn’t been set, are probably too high to prevent ill health in workers. Despite considering the evidence, the HSE’s Advisory Committee on Toxic Substances (ACTS), has decided NOT to take any action other than to recommend an awareness raising campaign for those exposed to dusts to highlight possible risks to health. However, a number of independent experts and the Trade Unions were not happy with this decision. And following the workshop at the recent BOHS Conference in Cardiff, I’m sure that many practising occupational hygienists feel that applying limits of 10 mg/m3 for inhalable dust and 4 mg/m3  for respirable dust is no longer appropriate.

In my experience there are very few workplaces where inhalable dust exposures exceed 10 mg/m3. For most common processes, it is usually “reasonably practicable” to reduce exposure well below this level by applying common engineering controls such as containment, partial containment and well designed local exhaust ventilation. And in some cases simpler measures such as improving housekeeping or the way the job is carried out, may be enough. So I don’t think that it would be too expensive for industry to work to a lower limit. The TUC has recommended values of 2.5 mg/m3 for the inhalable fraction and 1 mg/m3 for the respirable fraction of “low toxicity” dusts as interim limits. I think these are achievable in practice for most companies if they apply industry best practice. This seems a common sense approach which would reduce the risk to health for workers exposed to these dusts.

However, there there is a problem – there are a number  of “poorly soluble dusts of limited cytotoxicity”, to use the HSE’s preferred term, for which WELs have been established using the 10 and 4 mg/m3 values . For example, aluminium oxide, barium sulphate, cellulose, graphite, gypsum starch and titanium dioxide. There’s about 20 in all. If the HSE doesn’t reduce the limits for these substances, and there is no indication that they intend to do that, it may be difficult to convince employers that they need to work to a lower level than the legal limit.

I guess the best approach would be to argue that COSHH requires that even where a limit is set, the “principles of good control practice” set out in in schedule 2a, have to be applied. In my experience, in nearly all cases where we’ve carried out dust surveys there are usually simple measures that can be taken to reduce dust levels, even when exposures are below a WEL.  So, in most cases by implementing common sense measures and established industry good practice it should be possible to reduce exposure down to the TUCs recommended levels, even for those dusts where a WEL with a higher value exists.

Low Toxicity Dusts – Part 1

dust exposure

(Image source: BOHS)

Regulation 2 of COSHH1 states that any dust when present in the workplace at a concentration in air equal to or greater than 10 mg/m3
of inhalable dust or 4 mg/m3 of respirable (as a time-weighted average over an 8-hour period) is considered to be a substance hazardous to health. If the concentration of dust in a workplace exceeds these figures then the requirements of COSHH will apply, including the need to assess the risk to workers and to ensure exposure is prevented or adequately controlled.

The 10 and 4 mg/m3 values are NOT Workplace Exposure Limits (WELs), but, in practice, they are widely used as such by many occupational hygienists for “low toxicity dusts” where a WEL hasn’t been set. This seems like a reasonable thing too do, particularly as these values have been used where WELs have been set for dusts of low toxicity, such as aluminium oxide, barium sulphate and  titanium dioxide.

However, recently, serious doubts have been expressed as to whether this approach is valid and appropriate to protect the health of workers exposed to airborne dust. There is evidence from both animal experiments and industrial experience that relatively low exposure, well below these levels, to “low toxicity” dust (the UK Health and Safety Executive now prefer the term “poorly soluble dusts of limited cytotoxicity”) may cause adverse effects.

Snapshot[4]

At their annual Conference in Cardiff earlier this year, the British Occupational Hygiene Society (BOHS) held a workshop on “low toxicity dusts” to try to advance the debate. The presentations, which summarise the key points made by the speakers can be downloaded from the BOHS website here. The presentations by John Cherrie and Alistair Hay are particularly informative.

Exposure to high concentrations of any dust can overload the normal clearance mechanisms in the lung, leading to inflammation and possible lasting effects. In particular, there is evidence that exposure to many dusts can cause or worsen chronic obstructive pulmonary disease (COPD). According to HSE, 15% of the risk of chronic obstructive pulmonary disease (COPD) is attributable to gases, dusts, vapours, and fumes at work, and 4000 COPD-related deaths in England are due to workplace exposures. High lung burdens of “low toxicity dusts” can also prevent clearance of other, more toxic, particles, leading to a higher risk of other lung diseases.

Too much of any substance will cause harm. The question is, what is “too much”? Unfortunately, for “low toxicity dusts” the evidence is relatively limited.

In 1999 the HSE published a Contract Research Report of work carried out by the Institute of Occupational Medicine (IOM). They developed a mathematical model based on animal experiments  to estimate the no-adverse effect level (the NOAEL) for titanium dioxide, based on avoiding the impairment of dust clearance and the beginning of inflammation. Using the model they derived a human NOAEL of 1.3 mg/m3 .

In his presentation at the BOHS workshop Alastair hay discussed an IOM study on coal-miners, which found that 35 years exposure to 4 mg/m3 respirable could lead to 17% of non-smoking workers experiencing an FEV12 loss of almost a litre, compared with 10% in a non-dust exposed population

The HSE’s Advisory Committee on Toxic Substances (ACTS), considered low toxicity dusts in 2006/7. The outcome was that they decided to take no further action other than to recommend an awareness raising campaign for those exposed to dusts to highlight possible risks to health. A number of independent experts and the Trade Unions were not happy with this decision.

There is also concern about whether the mass concentration is the most appropriate way of evaluating the degree of risk from dust which is probably related to surface area. Exposure to small particles will have a greater effect than the same mass of larger particles of the same dust.

The following charts, extracted from John Cherrie’s presentation at the BOHS Conference show the relationships between pulmonary inflammation and mass (left hand chart) and surface area (right hand chart) for three different dusts

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The data was derived from Donaldson K, Brown D, Clouter A, et al. The pulmonary toxicology of ultrafine particles. J Aerosol Med 2002;15:213–220.

The charts show a fairly clear linear relationship between surface area and inflammation, irrespective of the type of dust.

I suspect that the majority of occupational hygienists who attended the workshop came away convinced that applying limits of 10 mg/m3
for inhalable dust and 4 mg/m3  for respirable dust, whether they are “official” or not, is no longer appropriate. So what limit should be applied to these dusts? I’ll return to this in another post.

Notes:

1 the Control of Substances Hazardous to Health Regulations

2 FEV1 is the “Forced expiratory volume in one second”. This is the amount of air that can forcefully exhaled in one second