De minimis or material? – The survival of the false dichotomy in industrial disease cases – Carder v Secretary of State for Health [2016] EWCA Civ 790


sep16We recently voiced questioned the use of the maxim ‘de minimis’ when proving causation in multi-exposure industrial disease claims (see here)[fusion_builder_container hundred_percent=”yes” overflow=”visible”][fusion_builder_row][fusion_builder_column type=”1_1″ background_position=”left top” background_color=”” border_size=”” border_color=”” border_style=”solid” spacing=”yes” background_image=”” background_repeat=”no-repeat” padding=”” margin_top=”0px” margin_bottom=”0px” class=”” id=”” animation_type=”” animation_speed=”0.3″ animation_direction=”left” hide_on_mobile=”no” center_content=”no” min_height=”none”][1]. It was suggested that in these types of claims the function of the maxim has been subverted.

Historically, de minimis was used as a blunt tool to exclude trifling matters from litigation. However, recent cases in the industrial disease arena have given it a broader role. This has been done by equating the finding that a defendant’s contributory factor is not de minimis, to meaning that factor is ‘material’ and so causative; that is to say to find that it “materially contributed” to a claimant’s damage. Materiali contribution has therefore been treated as the converse of de minimis, with no space for manoeuvre between the two.

In creating this false dichotomy, the term ‘de minimis’, which is by its very nature an impressionistic idea, undercuts the objective and scientific inquiry that should accompany any investigation into whether something is material or not. Further, it undermines the test of ‘materiality’ as set out by the House of Lords in Rothwell.[2] That is, whether or not the contributing factor makes the claimant “worse off”. The fact a contributing factor is not deemed to be ‘de minimis’, does not necessitate the conclusion that the contributing factor made the Claimant worse off.

By determining causation in relation to whether something is de minimis or it is not, the legal approach displays insufficiently clear reasoning and a lack of scientifically rigorous analysis in an area of law deeply rooted in medical and epidemiological research.

Carder in the High Court

The essential issue was illustrated in the first instance decision in Carder v Secretary of State for Health [2015] EWHC 2399 (QB). The relevant facts are that the Claimant developed asbestosis, and the Defendant contributed only 2.3% of the Claimant’s asbestos exposure.

The Claimant’s expert, Dr Rudd, suggested a figure of a 1% contribution to total asbestos exposure as the threshold below which any exposure could be viewed as de minimis in light of the overall exposure. He indicated that this was from a “common sense” point of view. This evidence supports the view that de minimis is an impressionistic term. The court then applied the false dichotomy to conclude that because the Defendant’s contribution was not de minimis, it was positively ‘material’ and so causative of the Claimant’s injury. To put it another way, causation was proven on the basis of an expert’s “common sense” view.

This was despite Dr Rudd’s assertion that the Claimant’s actual function and symptomology would not have been “measurably or demonstrably different’ if the Defendant’s contribution had not taken place. It is hard to reconcile the court’s approach with the test of materiality in Rothwell. It is not clear how on Dr Rudd’s evidence the Claimant in Carder had been made worse off.

It was on this basis that the case was brought before the Court of Appeal, providing a valuable opportunity to put to bed the false dichotomy of ‘de minimis or material’ and to provide further guidance on how to approach the concept of ‘materiality’. Unfortunately the court did neither.

Carder in the Court of Appeal

Lord Dyson MR delivered the decision of the court. Unfortunately ,the judgement accepts and reinforces the impressionistic use of de minimise as a test of causation .

Dr Rudd was asked four questions by counsel for the Defendant, in an effort to argue that the Claimant had not been made “worse off”, meaning the Defendant’s contribution was not material.

In answering, Dr Rudd explained that if the Defendant’s exposure had not taken place, the appearance of the Claimant’s lungs and his response to lung function testing would be no different. Nor would the subjective perception of the Claimant’s symptomology change and finally, the Claimant’s ability to cope with daily tasks would have been the same.

The Defendant’s case was therefore that the 2.3% exposure made no difference to the Claimant’s symptoms, disability or prognosis, and it followed that there was no actionable damage. Or to put it another way, the Claimant had not been made materially worse off by the Defendant’s exposure. It was not enough to merely contribute to the disease process, where that contribution made no other measureable difference to the Claimant.

This argument applies the test of materiality in Rothwell to a contribution to injury as to sole causation .

However, the decision was reached pursuant to a less principled line of reasoning. The Court of Appeal quoted Lord Reid in Bonnington[3]:

a contribution which comes within the exception de minimis…is not material, but I think that any contribution which does not fall within that exception must be material.

This passage explicitly sets out the false dichotomy. This, combined with what appears to be a paradoxical concession by the Defendant, was decisive of the case. At paragraph 28 the court stated Mr Kent [the Defendant] conceded that the…exposure, although very small, was material”.

It is not clear on what basis this concession was made given Defendants central argument.

it could have been conceded that the exposure was not de minimise in the traditional impressionistic sense ; but such a

concession should have been irrelevant. Whether or not the contribution was de minimis in this sense should not in and of itself be decisive of whether a Claimant was worse off as a result of that contribution. That conclusion should be reached pursuant to the medical evidence which was unequivocal on this point .

However, as a direct result of the false dichotomy, the concession was decisive. Lord Dyson stated at paragraph 39 that “there is a fundamental contradiction in the appellant’s [defendant’s] case”, because on the one hand the Defendant argued the contribution has made no difference to the Claimant’s symptoms, disability or prognosis, but on the other hand conceded that the 2.3% was material.

Lord Dyson continued at paragraph 40:

it is conceded that the increase was material i.e. not de minimis’. In my view, this concession is critical. In these circumstances, the judge was right to hold that Mr Carder was slightly worse off…this conclusion naturally followed from the appellant’s acceptance of the fact it was responsible for the 2.3% and that this was material.”

This is the starkest example yet of how the false dichotomy between materiality and de minimis is clouding proper legal and scientific analysis. The court did not consider in normative terms how Claimant could be “worse off” despite there being no measureable difference resulting from the Defendant’s contribution. Instead, the court relied almost entirely on the Defendant’s concession that the contribution was not de minimis (or as Mr Kent put it, that it was material) to conclude that the contribution was material and causative. This borders on circularity.


The Court of Appeal decision in Carder confirms that the time has come to dispose entirely of the use of the term ‘de minimis’ when proving causation in multiple exposure industrial disease claims.

A concession that something is not de minimis should not have necessitated the conclusion that the Claimant had been made worse off by the Defendant’s contribution. At most, it should have been taken as an acknowledgement that the contribution was not so trifling as to be ignored. This should not have impacted on a normative analysis of why the Claimant had or had not been made ‘worse off’, which is the test for materiality.

Even if there is some utility in using the term de minimis in order to emphasise a particular contribution is worthy of the court’s consideration, the confusion it is adding to the test of causation, the decisiveness afforded to the false dichotomy and the obfuscation of sound reasoning resulting from this means that it is best to dispense with the maxim altogether.

[1] ‘Is it time to disregard de minimis?’ Charles Feeny and Sammy Nanneh

[2] Rothwell v Chemical and Insulating Company Limited and others [2007] UKHL 39

[3] Bonnington Castings v Wardlaw [1956] AC 613

This article was co-authored by Charles Feeny and Sammy Nanneh[/fusion_builder_column][/fusion_builder_row][/fusion_builder_container]

Dust-Clouds and Dustbins: Should There Be a Regularity Requirement for Dust Exposure When Defining ‘Substantial’ Under Section 63 (1) Factories Act 1961?

This article originally appeared on the PI Brief Update website

dustIn cases where an employee is exposed to asbestos, a claim may be brought under the common law as well as pursuant to duties owed by the employer under various regulations and legislation. One example of such legislation is s.63 (1) Factories Act 1961, which provides that:

In every factory in which, in connection with any process carried on, there is given off any dust or fume or other impurity of such a character and to such extent as to be likely to be injurious or offensive to the persons employed, or any substantial quantity of dust of any kind, all practicable measures shall be taken to protect the persons employed against inhalation of the dust or fume or other impurity and to prevent its accumulating in any workroom…”

In McDonald v National Grid Electricity [fusion_builder_container hundred_percent=”yes” overflow=”visible”][fusion_builder_row][fusion_builder_column type=”1_1″ background_position=”left top” background_color=”” border_size=”” border_color=”” border_style=”solid” spacing=”yes” background_image=”” background_repeat=”no-repeat” padding=”” margin_top=”0px” margin_bottom=”0px” class=”” id=”” animation_type=”” animation_speed=”0.3″ animation_direction=”left” hide_on_mobile=”no” center_content=”no” min_height=”none”][2014] UKSC 53 the Claimant had worked as a lorry driver, frequently entering a power station to make collections, during which time he was exposed to asbestos. The Supreme Court considered s.69 (1) in depth, such as how to approach the need for a claimant to be a “person employed” and the meaning of “in connection with any process”. These two particular points are beyond the scope of this piece.

Lord Kerr, handing down the majority judgement, shed light on the approach to the meaning of ‘dust’ under s.63 (1). It was wrong to interpret s.63 (1) as requiring an employee to be exposed to a “substantial quantity of injurious dust”. This would be to conflate two separate and alternative limbs contained within the subsection.

Limb one, Lord Kerr stated, is concerned with exposure to ‘injurious dust’, irrespective of whether the quantity of that dust is substantial. On the other hand, limb two required a ‘substantial exposure to dust’, irrespective of whether that type of dust is known to be injurious.

Only if the answer is ‘yes’ to either limb will the court turn to asking if there were practicable measures the employer should have taken to protect against the exposure. If no such steps were taken, the employer is liable under s.63 (1).

The focus of this piece is the approach the law should take to defining ‘substantial’ under limb two of s.63 (1). It is argued that because the intended ambit of limb two is broad, s.63 (1) should be kept within normatively acceptable bounds by requiring ‘substantial’ to mean that any exposure exhibited a degree of regularity. One-off emissions resulting in dust-clouds should not per se fall within the definition of ‘substantial’.

Limb 1 vs. Limb 2 – a normative difference? 

It is worth asking why there is a dichotomy present in s.63 (1). Is it not simpler to conflate the two limbs, requiring a ‘substantial quantity of injurious dust’? Aside from the textual injustice of that approach, there is an important normative distinction to be made.

While limb one is concerned with dust known to directly harm an individual (a specific risk), such as asbestos, the ambit of limb two is a wider one, aimed at reducing general levels of dust in the workplace, with a desire to guard against the long-term risks of dust more generally. For example, one aim is to reduce long-term exposure to dust whose risks are currently unknown but could be revealed as harmful in the future. Limb two is not therefore concerned with freezing time to look at particular exposures to dust by specific individuals.

Limb one is aimed at protecting individuals from the specific risks of injurious dusts. This specificity to an individual means that an employer can only be liable where, in light of the state of knowledge at the time of exposure, it was reasonable for an employer to foresee that exposure to that specific type of dust would cause that particular employee injury, so as to require the employer to take protective action to protect them.

On the other hand, limb two’s aims are beyond the concern of any particular individual. Limb two therefore does not require any notion of reasonable foreseeability or state of knowledge to be satisfied.

McDonald supports thisanalysis in two key ways. First, the court unanimously agreed that the meaning of ‘substantial’ calls for a purely quantitative assessment. This is because the aim of limb two is to keep general workplace dust levels down. It does not involve looking at the nature of the dust itself nor the foreseeability of injury to an individual.

Second, the court concluded the employer’s duty under limb two is not dependent on the quantity of dust being considerable at the moment of inhalation. What is crucial to the meaning of ‘substantial’ is the quantity of dust in the workplace at any given time dust is released, not the time at which any inhalation occurs. This confirms that limb two is not concerned with the individual.

The majority held that there was insufficient evidence that the exposure in this case was substantial. Evidence of a ‘visible dust cloud’ was not enough. It was not clear such clouds were the only way of assessing dust levels at the time of exposure. This supports the conclusion that irregular dust-clouds, however visible, should not provide a basis for concluding an exposure was ‘substantial’. Stricter scientific approaches to quantification should be pursued, especially because limb two is not about any specific encounter between an individual and a visible dust-cloud.

If limb two aims to keep general workplace dust levels down, it is illogical to include highly irregular dust-clouds or one-off/chance exposures within the ambit of ‘substantial’. Any exposure should take place with a non-negligible degree of frequency and/or regularity. Only then can limb 2 serve its normative function of keeping workplace dust levels low.

As limb one already deals with claimants who are individually exposed to specifically injurious dust concentrations, there is no need for limb two to include infrequent but specific exposures. ‘Substantial’ should require a a minimum degree of regularity or frequency.

Moreover, limb two should not be used as an escape valve for claimants who have been unable to prove that an employer could foresee that a particular exposure to a specific dust would result in injury to the claimant. If a claimant could then rely on those same specific exposures to find a breach under limb two, without also showing some degree of frequency or regularity in the levels of workplace dust, that would render limb 1 superfluous.

Decisions since McDonald 

Smith v Portswood [2016] EWHC 939 (QB):

A former employee worked as a joiner for the defendant employer between 1973 and 1977. On the evidence, it was held that very occasionally the employee was required to cut and trim asbestos sheets. The exposure to asbestos would take place for around 10 minutes. The rarity of such occasions and the nature of the activity meant that the concentrations of asbestos exposure did not exceed the Health and Safety Executive’s permitted thresholds contained in Technical Data Note 13 (“TDN 13”).

This fact the TDN 13 thresholds were not exceeded meant that under limb one of s.63 (1), as well as under the common law, the employer could not have foreseen that the exposure was likely to be injurious to the Claimant. The Claimant was left to rely on limb two of s.63 (1), which does not require foreseeability.

In considering if the quantity of dust was ‘substantial’, the witness evidence stated that dust would “fly up into the air”. However, the judge held that much of the dust was removed using an extraction system so it was unlikely that dust-clouds would form. Further, given that there was no reliable method for measuring concentrations of dust, there was no basis on which to conclude the exposure was ‘substantial’ under s.63 (1). Essential considerations of both time and frequency of the exposure were missing.

This is a welcome endorsement of the need for a quantitative approach to the term ‘substantial’ as set out in McDonald. It appears that, as in McDonald, the absence of scientific quantitative evidence led to the conclusion that ‘substantial levels’ of dust had not been proven.

It appears the rarity of the exposures buttressed the judge’s conclusion that exposure was not substantial. This emphasis on the lack of frequency is the correct approach.

Any suggestion that the conclusion of ‘not substantial’ was based on it not being proven that a dust-cloud was visible should be rejected. After all, in McDonald the visibility of a dust-cloud was not decisive. It is frequency and regularity that should count.

The case also shows how a claimant was unable to circumvent its inability to establish liability under limb one (as foreseeability was not proven) by invoking limb two, when they were unable to properly quantify the levels of dust in the workplace.

Prater v British Motor Holding [2016]WL 03947474:

In this case the former employee had been exposed to asbestos while working as a panel beater between 1958 and 1975. The judge in this case adopted the two limb approach to s.63 (1), finding that both limbs were satisfied.

The evidence was that 30-35% of the employee’s work involved exposure to asbestos. The dust was described as being all over his clothing, which was not washed more than once a week. Further, there were no shower facilities. No steps were taken to reduce inhalation or accumulation of asbestos dust.

The judge held that when considering the meaning of ‘substantial’ under limb two, it was a factual question for the trial judge, depending on the evidence in the particular case. He found that the quantity of dust exposure during the Claimant’s employment was substantial. It was “the only quantitative assessment that can be made based on a common sense view of that evidence”. He noted that the dust given off was in such quantities “as to be visible in the air, including as a haze or smog”. The dust-cloud has made yet another irrelevant judicial appearance.

It is suggested that once again the key to this decision was the frequency of exposure. 30-35% of the employee’s work involved exposure to asbestos. Putting limb one aside, there was a frequent and regular high level of dust in the defendant’s workplace, with no steps taken to reduce it.

There is another point in Prater that supports the regularity requirement posited in this piece. The judge held that it did not matter that a quantity of asbestos found before the publication of TDN 13, which was also lower than the concentrations prescribed in TDN 13, could be substantial. This may be surprising but it is surely right. TDN 13 is used as a benchmark of foreseeability under limb one. It therefore does not come into play under limb two.

Substantial dust levels are not marked by any particular concentration of dust. Instead, the focus is on the regularity and frequency with which dust appears in the workplace. The normative underpinning is that an employer should seek to reduce this long-term dust level. Whether a particular individual is exposed to levels of asbestos which are higher than TDN 13, or not, is beside the point. As the judge put it, if an employer does not know whether there is any safe level of exposure, it makes perfect sense to say that the exposure must be reduced to the maximum extent practicable. Under limb two, the focus is on the steps of the employer, not any specific exposure of an employee.

Warne v Vinters-Armstrong Limited [2016] EWHC 1971 (QB);

Most recently, in this case the employee was exposed to asbestos dust during the course of his employment over 50 years ago. The single issue in the case was “how much asbestos the Claimant had been exposed to?” If it exceeded 25 f/ml years than the employer would be in breach of its common law duties to the employee. S.63 (1) was therefore not directly relevant.

However, it is interesting to note what the result should have been had a claim been brought pursuant to s.63 (1). On the facts, the Claimant had been exposed to asbestos dust when he tipped over a dustbin of asbestos to douse any fires that begun on the machine he was manning. This only occurred around 9 times a year. When the fires were doused, large dust-clouds would form which would drift away from the employee as they rose with the heat of the flames.

The judge concluded that the quantity of asbestos exposure was insufficient to create a foreseeable risk of injury, so that the employer was not in breach of its duty of care. This would mean that limb one of s.63 (1) would also not apply, as the foreseeability test was not satisfied. Would a limb two argument succeed? Despite the presence of a visible asbestos dust-cloud (which would quickly drift away), the important point is that the exposures were infrequent and irregular.

It may be argued that Warne represents a tough, middle of the road case. Difficult line drawing may need to take place to determine if nine instances of exposure are frequent enough to be ‘substantial’ under limb two of s.63 (1). It may be argued that nine times per year is not frequent enough to require the employer to take reduction measures. Limb two is blind to whether the dust is asbestos or any other dust. If dust from outside blew through the window nine times a year, would the law expect the employer to take dust-reducing measures? The bar must surely be higher.


In the context of asbestos claims it is very easy to conflate common law duties with regulations and legislation. There is a great deal of overlap between the different tests required under different heads of claim. Under s.63 (1) Factories Act 1961, there are two separate limbs. The first is not concerned with quantity. Its aim is to target specific cases where particular individuals have been affected by injurious dusts. Foreseeability of the employee’s injury is therefore key. In contrast, the normative importance of limb two is to encourage employers to keep workplace dust levels down. Quantity is key. As part of this quantitative assessment, it is essential to factor in frequency and regularity into the definition of the term ‘substantial’. This is far more important than the visibility of any dust-cloud. Without any regularity, it cannot be expected that an employer should take steps to reduce their dust levels. To hold otherwise is to ignore the function of limb two of s.63 (1).

Further commentary on this topic is provided by the authors at the Pro Vide Law website.

Charles Feeny & Sammy NannehContributing Editors at Pro-Vide Law[/fusion_builder_column][/fusion_builder_row][/fusion_builder_container]