Workplace Exposure Limits – The Problems for Demonstrating Compliance

Rachel Powis MSc CertOH LFOH – Occupational Hygiene Technical Manager (Envirochem)
Edited by Dr Alexander Bianchi CFFOH, FRSPH, DipOH, CChem, MRSC Scientific Advisor

Workplace Exposure Limits (WELs) form a fundamental part of the UK Control of
Substances Hazardous to Health (COSHH) regulations, and substances which have been
assigned a WEL are subject to the requirements of COSHH. However, demonstrating
compliance with these exposure limits can pose significant challenges both for employers
and businesses.

One of the main problems is the complexity of reliably assessing worker exposure levels and
making valid interpretations from what are often small data sets generated by typical
monitoring strategies. Even when comprehensively designed, worker exposure sampling
frequently offers only a snapshot of exposure occurring at a specific time. But we know that
wide variations in exposure levels can occur depending upon various factors such as
variance in job tasks and individual work practices (which can generate significant exposure
variability between workers), different exposure profiles such as are encountered in batch
production processes and, along with external influences including environmental factors
and workload, can result in considerable day-to-day variability.

Workplace exposure variability, whilst being dynamic in character, are accepted to conform
to a log-normal distribution. This distribution implies that a small but key number of
workers may be exposed to significantly higher levels of the hazardous substance
compared to the other data making up the spread. This can introduce a degree of
complexity to interpreting exposure results, as samples taken on one specific day under the
prevailing conditions at that time may not be likely to capture the full range of exposures
that workers may experience over longer periods of time.

To give some meaning to limited sampling data and help with navigating such issues, BS EN
689: Workplace Exposure – Measurement of Hazardous Substances – Strategy for Testing
Compliance with Occupational Exposure Limits
provides guidance on statistical methods
for demonstrating compliance. This is applied by using a derived benchmark known as the
“statistical lower confidence limit,” to assess whether a workplace is compliant with
exposure limits set by occupational health and safety regulations. For a sample pool of only
three results from workers who are considered to be similarly exposed to the hazard of
concern – often a number logistically achievable from a one-day sampling exercise – this
benchmark is calculated at 10% of the WEL value.

Demonstrating compliance, or conversely exceedance, therefore becomes arguably
simpler with very high or very low exposure profiles but becomes more challenging to
assess in cases where measured exposures fall within a central range of variability. In such
cases, demonstrating compliance with WELs requires additional monitoring efforts and
statistical analysis may be required to accurately evaluate results. The downside of course
is that this approach can be prohibitively costly and often offers no further benefit where
the goal is to ensure adequate control and protect worker health.

COSHH regulations place the responsibility on employers to control and minimise exposure
to hazardous substances in the workplace. This includes conducting risk assessments and
implementing control measures whilst being informed and guided by the sensible
application of monitoring and exposure assessment. Control of exposure is only considered
to be adequate when the Principles of Good Practice are applied, the WEL is not exceeded
and, for carcinogens, asthmagens and mutagens, exposure is reduced to as low as
reasonably practicable.

Therefore, WEL compliance only forms a part of what is required by law, and WELs taken in
isolation should not be considered a hard and fast line between safe and unsafe. In addition,
a further precautionary note is that these exposure limits are not always set at levels that
adequately ensure worker safety. For example, comparing a small number of UK WELs with
other respected international exposure limits (e.g. ACGIH TLVs) suggests a degree of non-alignment and raises the question that they may not reflect the latest scientific evidence
on health effects.

This apparent dissonance between WELs and international standards creates challenges
for businesses, especially those operating across international or global horizons, in both
adequately protecting employee health, especially where WEL compliance is being applied
as the primary indicator used to assess control. In many cases, companies operating
internationally insist that the Occupational Exposure Limits (OELs) applicable in the
countries where they are headquartered take precedence especially where they may be
more conservative than other OELs applicable in different legal jurisdictions. Moreover,
these requirements are often enshrined in company policies on a global scale. Therefore,
for a UK-based entity, it is crucial for employers to go beyond simply meeting the WELs on
several levels as well as taking all necessary proactive measures to ensure the safety and
well-being of their workers and compliance with regulatory requirements in their own host

Indeed, addressing these challenges requires a comprehensive approach that goes beyond
sampling data. This can include implementing additional control measures for continuous
improvement, consulting industry and specialist trade bodies and independent expert
panels in order to stay up to date on best available control technologies. It also includes
reviewing existing control measures with the Principles of Good Practice in mind.
Additionally, employers should stay informed about updates to international standards
that impact their businesses directly as well as scientific research regarding health effects.
By following these guidelines and taking a proactive approach to managing workplace
exposure, employers can demonstrate their commitment to employee health and safety
while also mitigating potential legal risks and reputational damage.

Addressing the complexities of demonstrating compliance with WELs requires a
multifaceted approach that considers the variability of workplace exposures, reviews
controls against a range of indicators, and goes beyond minimum regulatory requirements.
In many cases it also involves continually striving to meet ‘regulatory and industry best
practices’, and, increasingly for companies operating internationally, achieving full range
compliance across even broader horizons.

In summary, more than ever, engaging with occupational hygiene professionals and
seeking their expertise can help businesses navigate the complexities of workplace
exposures and ensure that their employees are adequately protected. While compliance
with WELs is an important aspect of protecting workers from hazardous substances, it is
not the sole indicator of occupational health and safety performance, and employers have
a responsibility to go beyond these limits. By proactively addressing the limitations of WEL-focused sampling strategies and combining other benchmarks, such as the Principles of
Good Practice employers can ensure a more comprehensive approach to managing
hazardous substances and protecting the health and safety of their workers while
delivering sound compliance with the COSHH regulations.

Envirochem is passionate about creating better health outcomes for your personnel, who
in turn will create better outcomes for your business. Our goal is to help you build a healthier
and more productive business through our expertise in Human Health & Environmental
testing & consultancy.

Our specialists work as trusted advisors, becoming embedded in clients, whether we are
scoping out occupational hygiene dust monitoring and consultancy, noise assessments or
asbestos sampling & analysis. Supporting beyond an initial scope, we help you identify
other potential sources of risk which also may need due consideration-from dust explosions
and DSEAR to chemical testing in soil samples. Envirochem is your extended team when it
comes to making your people safer.

Our occupational hygiene monitoring programs can provide you with useful baseline data
across your sites’ operations. This only takes you so far on your safety journey towards best
practice. To make true, continuous improvement in worker health, real world, actionable
steps which facilitate positive change are required. Envirochem can provide expertise and
advice, tailored to your specific needs and site requirements, through bespoke control
audits. The worker exposure data we collect will be used in conjunction with our
consultancy experience, to help determine what you can do to effect the changes you need
to make.

To book a complimentary site visit, where we can discuss your requirements in detail, please

Dust Exposure in Flour Milling and Bakeries: Occupational Hygiene Challenges in the Workplace

Written by Rachel Powis MSc CertOH LFOH – Occupational Hygiene Technical Manager (Envirochem)
Edited by Dr Alexander Bianchi CFFOH, FRSPH, DipOH, CChem, MRSC Scientific Advisor

The adverse health effects of flour dust exposure have been known at least as far back as
the 1700s, when flour millers’ lung was documented by Bernardo Ramazzini, a Florentine
physician. Since then, various research and exposure studies have been conducted to try
to better understand the impact of flour dust on the human respiratory system, and to get
to grips with its effect on the overall health of workers in the milling and baking industry.

It was specifically in the 1930s that allergic responses to flour dust were extensively
examined in bakers, when conditions such as “Baker’s Lung” were highlighted. In addition,
the observation of skin (i.e. dermal) responses to dust exposure in tandem with respiratory
(asthma) symptoms observed within cohorts of bakery workers added to existing evidence
of its potential as a sensitiser. Moreover, when bakery workers showed an absence of
symptoms following time off work away from the bakery, the link between flour dust
exposure and health effects was significant. Remarkably, even now in the early part of the
21st century, flour dust exposure remains a leading cause of respiratory disease. For
example, in 2021, it was cited by the UK SWORD reporting scheme (i.e. Surveillance of Work Related and Occupational Respiratory Disease) as a leading cause of newly reported
respiratory disease, second only to asbestos.

Occupational exposure to flour dust is commonly associated with a wide range of
respiratory ill-health conditions. Rhinitis is a common complaint as well as a “marker
symptom”, and typically precedes the more severe asthma and chronic bronchitis
symptoms associated with “Baker’s Lung”. At a deeper level, these health effects are
influenced by various factors such as the type of flour, the dose, duration of exposure,
individual responses and susceptibility, and the occupationally determined environmental

Numerous studies suggest that ill-health responses are indeed more complex than simply
reactions to flour dust itself; in addition to flour, enzymes – often used within improvers –
and allergens – such as Aspergillus fungi – contribute to respiratory sensitisation and
symptoms. The risk can be particularly high during the milling process due to the high
volume of flour handled and additional risk factors from co-associated biological agents
within with the raw materials undergoing processing. Furthermore, these can be
encountered during a range of bakery tasks, from manual hopper additions to sieving and
surface dusting, and tied to flour handling and agitation processes which in turn create
airborne dusts. Therefore, the prioritisation of occupational hygiene exposure control
measures throughout the industry remains vitally important to minimise workers’ exposure
and mitigate a range of potential health effects associated with the consequent risk of
serious respiratory and skin diseases.

Most occupational exposure limits for flour dust are set as “Inhalable dust”, and 8-hour TWA
(Time-Weighted Average) exposure limits vary significantly from the ACGIH (American
Conference of Governmental Industrial Hygienists) TLV (Threshold Limit Value) of 0.5
mg.m-3 to the UK’s Health and Safety Executive WEL (Workplace Exposure Limit) of 10
mg.m-3. However, the literature records that ill-health effects have been reported at
exposures occurring below 0.5 mg.m-3 in some instances, indicating that first order
compliance with set occupational exposure limits may not in of itself be adequately
protective of health. Importantly, it underscores the critical significance of controlling
exposure to flour dust in the workplace as far as possible through application of ‘good
practice’ hygiene controls and associated measures.

The concept is not a new one; indeed, it is central to the ‘control and reduce’ philosophy of
the UK COSHH regulations, whereby emphasis on driving down exposures to as low as
reasonably practicable (and in real terms, meaningfully below applicable exposure limits)
applies for all forms of occupational sensitisers – for which flour dust most certainly has
been identified as. Consequently, it is crucial for flour milling and bakery facilities to
prioritise their occupational hygiene measures such as to minimise dust exposure. This is
essential to both protect their workers’ health and demonstrate sustainable and viable
compliance with regulations. Such occupational hygiene interventions include the initial
identification and recognition of all the key hazards and risks within the workplace followed
by thorough evaluation and monitoring of exposure levels. Moreover, above all, it requires
the full implementation of suitable and sufficient control measureswhich can offer genuine
and reliable long-term protection to all potentially-exposed workers.

Despite the inherent limitations with workplace sampling for direct comparison against
occupational exposure limits for flour dust (i.e. from a standpoint of health protection), the
effective and timely monitoring of air quality and dust levels in the milling and bakery
facilities is essential. How else can we understand exposure and identify any areas that may
require additional attention or improvement? Monitoring is an excellent tool for ongoing
exposure performance assessment and properly applied should drive ongoing commitment
towards continuous improvement.

Through such an approach the industry can gain insights to help create safer and healthier
environments for bakery workers, ultimately reducing the risk of serious occupational
health issues associated with flour dust exposure. In practical terms, HSE guidance suggests
that exposures of below 2 mg.m-3 (as an 8-hr TWA) should be reasonably achievable in any
case within bakeries when they apply good practice controls with exposure reduction
measures in place. However, this may be assumed or misapplied as a proxy exposure limit
or target level of exposure, and to that extent the HSE caution that meeting this level of
exposure may not in itself be indicative that good practice is in place. The guidance is clear;
the industry must demonstrate competence and capability in pushing exposure as low as is

Within many bakeries today, recent technological developments such as specialist “lowdust” flours have been explored largely to help achieve significant improvements for
reducing worker exposure. A 2023 study suggested an exposure reduction of up to 86%
during sieving was achievable; however, as a word of note, the composition of low dust
flours may render them unsuitable for specific applications and often comes with higher

Nonetheless, the implementation of effective dust control measures does not have to be
overly complex and costly. Simple control measures, such as reducing the amount of flour
used for dredging and placing lids on mixers can make large reductions in dust exposure
throughout bakeries. Similarly, sleeves surrounding transportation ducting, coupled with a
robust programme of equipment maintenance, have been assessed to significantly reduce
exposure for millers.

These measures, paired with regular competency training and the targeted use of personal
protective equipment for peak exposure tasks that cannot be avoided, form the backbone
of a successful programme for reducing occupational exposure. Importantly, the success
of control strategies is also often reliant onworker “buy in” and desirable behaviours, which
have a profound effect on individual exposures. For example, many cleaning activities still
rely on ‘high-dust generating’ dry sweeping which can lead to excessive exposures during
clean-up work and, frustratingly, undermine efforts targeted on control within routine
processes. The widespread use of archaic dry sweeping methods is possibly due to a lack of
awareness about best practices or oversight from employers and employees alike.
Therefore, training and education programs should always be implemented at the same
time across all levels within organisations. Effective control emphasises e3nsuring that
workers are aware of the health risks associated with flour dust and are equipped with the
knowledge and skills (and equipment) to minimise their exposure.

Awareness, however, is not the only barrier to effective control. Although commonly seen
throughout bakery facilities, air extraction fitted with moveable capture hoods are often
not well suited to manage sieving or surface dusting as they depend heavily on appropriate
positioning, which can be difficult to achieve. Alternative enclosure-type extractions
generally offer better control and have an advantage of not being dependant on user or
physical and area restrictions. Identifying suitable controls, therefore, involves both
technical and user input to find options which are suited both to the process and

Not least, worker health surveillance makes up an important component in overall
management of exposures by facilitating early detection of any individual potential health
effects on workers. Regular health surveillance should be conducted for workers in flour
milling facilities to monitor and identify any respiratory and skin symptoms or diseases that
may be linked to flour exposure. Health surveillance also plays a vital role in helping with
early intervention and treatment, as well as supporting occupational hygiene in assessing
the effectiveness of control measures in place. From a broader perspective, regular reviews
and information sharing between occupational hygiene and health professions is
advocated to fully understand ill-health risks and make targeted control interventions
where needed.

Envirochem has considerable expertise in occupational hygiene matters with respect to
dust, noise, and manual handling across a multitude of industries including the food sector.
We are passionate about creating better health outcomes for your personnel, who in turn
will create better outcomes for your business. Our goal is to help you build a healthier and
more productive business through our expertise in Human Health & Environmental testing
& consultancy.

Our specialists work as trusted advisors, supporting and assisting clients directly, whether
scoping occupational hygiene dust monitoring and consultancy, or noise assessments or
asbestos sampling. Supporting beyond the level of initial scope, we help clients identify
other potential sources of health exposure risk which also may require due consideration, spanning from noise and vibration hazards to dust explosions and DSEAR. Envirochem is
your extended team when it comes to making your people safer.

Our occupational hygiene monitoring programs can provide you with useful baseline data
across your operations. This only takes you so far on your safety journey towards best
practice. We are committed to assist you in making quality, continuous improvements in
worker health with real-world actionable steps which facilitate the positive changes that
are required. Envirochem can provide expertise and advice, tailored to your specific needs
and site requirements, through bespoke control audits. The worker exposure data we
collect will be used in conjunction with our consultancy experience, to help determine what
you can do to effect the changes you need to make.

For a free site scoping meeting, please contact us in confidence at:

Elms, Robinson, Rahman & Garrod (2005), Exposure to Flour Dust in UK Bakeries: Current
Use of Control Measures, The Annals of Occupational Hygiene, Volume 49, Issue 1, 2005
Daniels, Iskander, Seed, Carder & van Tongeren (2021), The Health and Occupational
Research (THOR) Network Annual Report, Centre for Occupational and Environmental
Health, University of Manchester
Martinelli A, Salamon F, Scapellato ML, Trevisan A, Vianello L, Bizzotto R, Crivellaro MA,
Carrieri M (2020) Occupational Exposure to Flour Dust. Exposure Assessment and
Effectiveness of Control Measures. International Journal of Environmental Research and
Public Health, Volume 17, Issue 14, 2020
Griffin, Fishwick, Elms, & Curran (2001), Respiratory symptoms and wheat flour exposure: a
study of flour millers, Journal of Occupational Medicine, Volume 51, Issue 2, 2001, p141-
Pocock, Hall, Bennett, Darnton, Molloy, Laboratory study of the effectiveness of
substituting traditional wheat flour with low dust flour and use of different sieve designs as
controls to reduce exposure to inhalable flour dust in commercial bakeries, Annals of Work
Exposures and Health, Volume 67, Issue 9, 2023, P1081–1087

Envirochem now offers a Fit2Fit accredited face fit testing service!

An inadequate fit will significantly reduce the protection provided by the RPE and may lead to serious immediate and long-term health problems.

Quantitative face fit testing can be carried out both at our head office in Fareham or on site.

Qualitative face fit testing can also be undertaken if required.

Types of tight fitting masks that can be tested:
• Half Face Ori-Nasal Respirators
• Full Face Respirators
• P3 Disposable Half Masks

If there are any other types of masks you would like tested and you are unsure
please don’t hesitate to ask.

Notes for candidates:
• All operatives must be clean shaven
• All operatives must refrain from eating or drinking for 1 hour before their test
• All operatives must refrain from smoking for an hour before their test
• Testing should be carried out every 1-2 years
• Re-tests should be undertaken if operatives face shape changes (i.e due to major
dental work/weight loss etc.)

Face fit testing procedure (according to HSE INDG479):
• Operatives will don their mask
• Operatives will then be required to undergo various exercises
• There are 7 exercises taking 80 seconds each.
• Operatives need to pass each exercise consecutively to gain a pass

Please call 01329 287 777 or complete the form below if you would like further information or a free quotation:

Contact Envirochem now

Environmental Perimeter Monitoring in Canary Wharf, London.

We have this week been working with one of our longstanding clients in Canary Wharf during the demolition of the building in the picture above.

What are we doing?

We have set up 3 perimeter particulate monitors on site measuring PM10 levels before the demolition phase and during the demolition.

What does this give us?

This way we can determine background readings within the area prior to the demolition to assess whether any limits are breached during the demolition and if they could be attributed to external factors or as a direct result of work on site.

The monitors are located on the perimeter of the demolition site, on sides that are neighbouring housing, businesses or roads and areas that the public readily use.

Benefits to the client.

The client has been set up to receive live alerts direct to the site manager’s mobile and email if a limit is exceeded, to ensure they can rectify any of the activities causing the issue at source.

The limits used are in accordance with the Tower Hamlets Environmental Protection Division Guidance. We will be sending monthly reports to our client who in turn will pass this on to Tower Hamlets EPO. Tower Hamlets will also be notified of any exceedances within 24 hours of the alert. This way our client is constantly aware of the levels and stays compliant with them.

For more information and to contact us about all our Occupational Hygiene Services please call on 01329 287 777 or fill out the for below:

Contact Envirochem now

What does Water testing entail:

Testing for coliform bacteria and E.coli are the most important routine microbiological analysis carried out on drinking water. These tests provide a sensitive means for detecting faecal contamination, for assessing raw water quality, the effectiveness of water treatment and disinfection, and monitoring water quality in distribution.

Why carry out Water testing:

Recreational water such as Pools and SPAs – can be easily get Infectious agents introduced into them via bathers, from dirt entering the pool or from the water source itself. Once in the spa pool, conditions often exist for these infectious agents to grow and proliferate.

Drinking water or potable water – To ensure water is safe enough to be consumed by humans or used with low risk of immediate or long term harm.

Environmental Water – Lakes, rivers and seas are used for a variety of recreational activities including swimming, diving, fishing and sailing. If these activities are to be enjoyed safely, attention must be given to health hazards such as sewage pollution and excessive growth of toxic cyanobacteria, as well as to the prevention of accidents. EC bathing water directive (2006/7/EC).

What we can offer:

Envirochem routinely carry out a variety of tests including:

For recreational water:

UKAS Accredited tests:

  • Total coliforms
  • E.coli
  • Total viable counts 1 days at 37°C
  • Pseudomonas aeruginosa
  • Legionella

For Drinking water or Potable water:

UKAS Accredited tests:

  • Total coliforms
  • E.coli
  • Total viable counts 2 days at 37°C
  • Total viable counts 3 days at 22°C
  • Pseudomonas aeruginosa

For Environmental Water:

Relevant tests:

  • Total coliforms
  • E.coli
  • Faecal streptococci

If you would like more information or you think you may require testing please call us on 01329 287 777 or fill out the form below.

Contact Envirochem now

Local Exhaust Ventilation (LEV) Testing.

What is LEV Testing:

Local exhaust ventilation (LEV) checks, help control the release of hazardous airborne substances from a process into the workplace environment.

Why carry out LEV testing:

The aim of LEV checking is to control the emission as close as possible to the point of release, and prevent it from entering the air of the workplace.

Who should carry out LEV Testing:

Anywhere with extraction units and/or that produces fumes, a few examples of workplaces and processes include:

  • Wood and carpentry manufacturers
  • MOT Stations
  • Restaurants with exhaust ventilation units
  • Industrial processes that produce paint fumes and solder fumes
  • Shot blasting and sand blasting processes
  • Air conditioning units
  • Furniture makers  

What we can offer:

Envirochem routinely undertake LEV checks for many clients on equipment including:

  • Fume cabinets
  • Spray booths
  • Dust extract systems
  • Air conditioning units
  • Exhaust ventilation units
  • Extractor fan units

These should be tested 14 monthly or after any modifications, as specified within the Health and Safety Executive’s HSE Guidance Notes HS(G)54 and HS(G)37.

We produce thorough reports detailing duct velocities static pressures and flow rates and make comments on any observed changes in the system reading or their possible causes.

For more information or to contact us please call on 01329 287 777 or fill out the form below;

Contact Envirochem now

Where is Lead found?

Why is Lead in paint?

Lead was used in paint to help speed up the drying process but also for visual properties. It also increased the durability of paint once applied.


Why test for Lead in paint?


The body can absorb lead that is breathed in, such as in the form of dust or fumes and if you swallow anything containing lead.

Exposure can lead to changes in your blood which may cause anaemia and it can have effects on your nervous system and kidneys.


Who should test?

Those at the highest risk of exposure are those that carry out industrial processes such as blast/burning removal of lead paint, lead smelting and many more that create lead dust, vapour or fumes.

However, even individuals or contractors stripping lead paint from windows, doors and frames from homes and workplaces can lead to exposure.


What we can offer:

Envirochem can offer UKAS accredited Lead in paint analysis and we can attend site and sample for you or alternatively we offer self-sampling kits for you to sample yourself to send to us for analysis.


For more information please contact us on 01329 287 777 or fill out the form below:


Contact Envirochem now




Hi-tech machines and instrumentation


Here at Envirochem, we have a wide range of Hi-tech machines and instrumentation, and use the most up to date scientific techniques.


This allows us to offer the best possible services, fast turnaround times and a large selection of testing and analysis options.


For more information and how we can help you call us on 01329 287 777 or fill out the form below;


Contact Envirochem now

Leak Air Testing on the perimeter of negative pressure units to an asbestos enclosure.

We were recently commissioned to carry out Leak Air Testing on the perimeter of negative pressure units to an asbestos enclosure, this is to  ensure that an elevated level of airborne fibres are extracted from the enclosure by the negative pressure units and there are no leaks.

Envirochem offer the full range of asbestos air monitoring services geared specifically to meet the requirements of your project, in accordance with HSG 248.

Our growing fleet of asbestos analysts are provided with fully equipped mobile laboratories allowing for on-site analysis of air samples and instant certification upon completion of analytical monitoring.

For more information call us on 01329 287 777 or fill out the form below:

Contact Envirochem now

We have recently achieved Accreditation status as a Fit2Fit Respiratory Equipment Fit Test Provider.

Respiratory Protective Equipment (RPE) is essential for Health and Safety. We carry out examination and Face Fit Testing of RPE in order to determine the suitability of the protective equipment.


And we have recently achieved Accreditation status as a Fit2Fit Respiratory Equipment Fit test Provider.


For more information and all our services please call on 01329 287 777 or fill out the form below;


Contact Envirochem now