Chris Packham looks at chemicals in the workplace and their management, with particular emphasis on skin exposure and its consequences.

We encounter chemicals every day, often without even considering them as such. Indeed, we are made up of a myriad of different chemicals, many of which in certain circumstances could be considered as hazardous, either to others or to ourselves. The reality is that everything is comprised of one or more chemicals and may be beneficial or harmful, depending upon the circumstances under which we encounter it or its effects on our environment.

This being the case, how can we ensure that chemicals within our working environment do not cause harm?

Firstly, is this an important issue when considering worker safety and health? The answer has to be a resounding yes. We do not know precisely how much damage to health is caused worldwide due to exposure to chemicals, but the statistics that we do have for many countries indicate that the total effect must be enormous. Statistics from the UK show that occupationally induced ill health causes an estimated 31,000 fatalities every year, many of which will be due to exposure to chemicals. Our concern should be with workplace exposure to chemicals that can cause damage to health and how we manage this so that harm does not occur; however, this is not as simple as many assume. Essentially there are three routes by which chemical exposure can occur, these being inhalation, ingestion and through the skin.


Traditionally, when considering chemicals in a working environment and their effect on those present in that environment, attention has concentrated upon inhalation as the route of exposure and uptake. There has been an immense amount of research into inhalation exposure and its effects. This has resulted in methods for monitoring and measuring, workplace exposure limits, and methods for controlling airborne chemicals, such as local extraction and respiratory protective equipment (RPE). It has been common practice to consider inhalation in isolation, but as this article will show this is frequently not correct.


Ingestion of chemicals and their effects on health are frequently not included in our evaluation of risks to health in the workplace. By ‘ingestion’ we do not mean what is consumed in the canteen, but what is ingested unintentionally through the oesophagus, stomach and digestive tract. Here again we cannot consider ingestion in isolation, as we will see when we consider causes of systemic toxic effects due to exposure to chemicals.

Skin exposure

Skin exposure is often considered to be of lesser significance compared to the effects of inhalation. It is common to find views such as a skin problem being ‘just a rash’ and therefore not of any great significance when compared with respiratory issues. If that were the case why do the EU regulations on classification, packaging and labelling contain the Hazard Statement ‘H310 – Fatal in contact with skin’? After all, just a few drops of dimethyl mercury on her gloved hand was sufficient to kill Professor Wetterhahn, an inspired researcher, who tragically died from acute mercury poisoning in 1997.

The reality is that statistics show occupational skin diseases to be more numerous than respiratory diseases, with the exception of asbestos and non-chemical related skin cancer. The following statement serves to illustrate the dangers of skin exposure:

“Both the number of cases and the rate of skin diseases in the US exceed recordable respiratory illnesses. In 2006, there were 41,400 recordable skin diseases reported by the Bureau of Labor Statistics 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.” – OSHA Technical Manual, Section II, Chapter 2.

This indicates that occupational skin diseases outnumbered respiratory diseases at a ratio of 2.36:1.

When in 2011 the World Health Organization held a workshop on the global prevalence of occupational skin disease, their conclusion was:

“Occupational skin diseases are among the three most frequent groups of occupational diseases. … However, occupational skin diseases have attracted relatively little attention in the global and national agendas for prevention of occupational and work-related diseases. – World Health Organisation Global Workshop, Geneva, February, 2011.

The EU Agency for Safety and Health at Work has stated:

“Occupational skin diseases are estimated to cost the EU €600 million each year, resulting in around three million lost working days. They affect virtually all industry and business sectors and force many workers to change jobs.” – European Agency for Safety and Health at Work, Fact Sheet no. 40.

Regarding national statistics, on which this statement was based, the European Dermatology Forum has stated:

“National registries are usually incomplete as a result of under diagnosis and underreporting of the disease. The incidence of occupational skin diseases in Europe may be underestimated by 10 to 50 times.” – from European Dermatology Forum White Book –Skin Diseases in Europe.

It is worth noting that the comment by the WHO about skin diseases attracted relatively little attention. While this is now changing, the emphasis on the training of occupational health and safety practitioners is still heavily biased towards respiratory exposure and its management. Indeed, in the UK it is still possible to qualify as a certified occupational hygienist without having completed any training on occupational skin exposure and its management. Some of the training that is provided is out of date and may even contain significant errors.

We need also to recognise that skin uptake can represent a potential risk of the exposed person suffering from systemic toxic damage. Skin uptake can be the more important route.

“In many instances dermal exposure is the principal route of exposure, especially for chemicals that are relatively non-volatile. For example, biological monitoring results of coke oven workers coupled with air monitoring of the employees’ exposure demonstrated that 51% of the average total dose of benzo[a]pyrene adsorbed by coke oven workers occurred via skin contact. Studies of employees in the rubber industry suggest that exposure to genotoxic chemicals present in the workplace is greater via the skin than via the lung.” – OSHA Technical Manual, Section II, Chapter 2.

One study even indicated that even if the level of airborne exposure were below the regulatory limit, there might still be a risk of damage to health due to skin uptake from the airborne chemical.

“Air threshold limits are insufficient to prevent adverse health effects in the case of contact with substances with a high dermal absorption potential.” – Drexler H, Skin protection and percutaneous absorption of chemical hazards, International Archives of Occupational and Environmental Health (2003) 76:359-361.

This can also work in the reverse direction, i.e. skin exposure may initiate respiratory problems.

“Although respiratory exposures have been the primary concern with isocyanates, skin exposure can also occur and may contribute to sensitisation and asthma.” – Skin Exposure to Aliphatic Polyisocyanates in the Auto Body Repair and Refinishing Industry: A Qualitative Assessment, Liu Y et al, Annals of Occupational Hygiene, 2007, 51, 429-439.

In his doctoral thesis in 2001, titled Genotoxic Exposure and Biological Effects in the Rubber Manufacturing Industry – Relevance of the Dermal Route, Roel Vermeulen stated:

“Little attention has been paid to dermal exposure in this particular industry. Falck et al and Kilpikari suggested in the early 1980s that dermal absorption of chemical compounds could play an important part in the rubber industry. Direct evidence for this hypothesis was found in a study by Bros et al in an aircraft tyre retreading company, where a direct relation was found between dermal exposure to cyclohexane soluble matter and urinary mutagenicity, while no relation was found between urinary mutagenicity and rubber particulates and fumes in air.”


We need to recognise that in many situations we will be dealing with exposure from more than one route. This is particularly significant when chemicals can be absorbed through the skin and initiate systemic reactions. The fact is that for systemic damage what is important is the total dose reaching the target organ, irrespective of the route of uptake. So what we need to identify is the combined uptake of all three routes: inhalation, dermal and ingestion. One of the immediate consequences of this is that, for many chemicals, the concept that ‘ensuring airborne exposure is below the prescribed regulatory level represents adequate control’ may not be valid in terms of the true risk of damage to health. It may be necessary for regulatory compliance, but should the combination of the uptake of the three routes be sufficient to cause systemic damage, worker health can be severely compromised. As a consequence, considering each of the three routes in isolation is no longer an acceptable approach.

The problem now arises as to how we can develop a comprehensive risk assessment approach, combining the data on all three routes. Unfortunately very little seems to exist in terms of scientific studies or guidance on this. At the present time our only reliable technique appears to be that of biological monitoring of workers to establish their level of exposure. While this may not, of itself, indicate the significance of each route of exposure, it will indicate whether the total uptake is significant so that further investigation can be conducted to establish how this exposure is occurring.

Assessing the risk

If we are to prevent damage to health due to chemical exposure what we need first is to identify the chemicals present to which the worker may be exposed, the hazards that these represent and the routes and importance of any actual or potential exposure. We call this a risk assessment. Many varied and sometimes complicated definitions of what is meant by risk assessment are to be found. Perhaps the simplest and best is that provided by the EU Agency for Safety and Health at Work:

“A risk assessment is nothing more than a careful examination of what, in your work, could cause harm to people, so that you can weigh up whether you have taken enough precautions or should do more to prevent harm.” – Taken from: “Good Practice Information Provided by EU-OSHA”, September 2009.

If our risk assessment is to be valid and help us in understanding what is needed to adequately protect the health of the workforce, we need to ensure that it reflects the real workplace conditions. We need accurate information on:

  • The real hazard presented by the chemicals when they are actually used
  • The extent of the exposure
  • Any additional factors, such as ambient temperature and humidity

In addition, environmental conditions can significantly influence the possibility of damage to health occurring due to chemical exposure.

What is the hazard?

One could say that there is no such thing as a ‘good’ or ‘bad’ chemical. A ‘bad’ chemical is one in the wrong place at the wrong strength and at the wrong time. Two examples may help to illustrate this concept. Hydrofluoric acid is highly hazardous if in contact with the human body. In certain industries, however, it has specific beneficial uses. Water is not normally considered a ‘bad’ chemical, yet excessive skin exposure to water is one of the most common causes of occupational contact dermatitis. So both chemicals can be ‘good’ or ‘bad’ depending upon the circumstances. The same can be applied to practically every chemical known to man.

We generally purchase chemicals to use for a particular purpose. In using them we will almost always initiate some change in their properties. What this suggests is that we have to discard our traditional approach to chemicals and their hazards, such as might be indicated by the hazard statement found on the safety data sheet. Instead our concern must lie with the real hazard presented to the persons potentially exposed to the chemical when it is used. In other words, our primary concern must be with the task. To identify the hazard for our risk assessment we need to know which chemicals are present, how they are being used, how this affects their potential to cause us harm and the nature of that harm. Only when we have this information can we start to assess the risk that harm will occur as a result of their use during the particular task for which the risk assessment is being carried out.

Take, as an example, the situation where a degreasing tank filled with toluene is being used to clean and degrease items of equipment that have been returned to the factory for repair or refurbishing. Each time one of these articles is placed into the tank chemicals will be removed from the article being cleaned. This will change the actual make-up of the chemical in the tank. It may well be that we do not have information on the nature of what has been removed, so the characteristics of the contents of the tank will become increasingly uncertain as successive items of equipment are processed. So, for how long would a risk assessment for toluene remain a valid risk assessment for the task of degreasing and cleaning?

Just to emphasise this point, in the latest edition of his book on patch testing for skin allergies, de Groot lists some 4,350 chemicals, most of which will never have been listed as H317 – May cause an allergic skin reaction.

If worker exposure could occur how do we assess the hazard and risk of damage to health? It should be obvious that simply taking what is on the safety data sheet is not an acceptable basis and can all too often result in an invalid risk assessment.

A further complication arises, however, in that other factors can affect both the properties of the chemicals and the potential for these to cause damage to health. Ambient conditions, in particular, can affect both properties and effect if skin exposure occurs.

What this means is that risk assessment has to be task based. The flow chart illustrates the suggested elements of a risk assessment.

Consider what we term stainless steel. This is a combination of steel, chrome and nickel. Nickel is one of our most common skin sensitisers. It has been estimated that one person in 10 is allergic to nickel, yet almost all of these will be able to handle stainless steel without any skin reaction, as the nickel is so tightly bound into the alloy that no molecules are being released, meaning nothing enters the skin to initiate a reaction. In other words, the nickel is not bioavailable. In processing a piece of stainless steel, however, it is possible for this to start releasing nickel, in which case any contact with the nickel sensitised person could result in allergic contact dermatitis. Just to add to the complexity, a certain threshold of exposure is needed to initiate the allergic reaction. The skin exposure might not be sufficient on its own, but combined with nickel uptake from ingested food there might, at least in theory, be sufficient levels for a reaction. In such an event we may be faced with a combination of occupational exposure of the skin combined with non-occupational exposure due to ingestion.


What this article has hopefully made clear is that the ‘traditional’ approach to risk assessment and exposure management for skin, based on hazard statements shown on safety data sheets, is not really fit for purpose. Perhaps it is time to review how we approach the complexities of skin exposure in the working environment, so that we can start to reduce the high level of occupational ill health caused by skin exposure.

Published: 20th Jul 2015 in Health and Safety International