Monitoring skin exposure to chemicals

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Inhalation is normally considered to be the main route by which chemicals can enter the body. Most industrial processes where chemicals are used will create airborne dust clouds or lead to the evolution of vapours and gases which are readily inhaled and then absorbed into the bloodstream via the respiratory system. However, in some cases there is a potential risk from absorption of substances through the skin following dermal exposure, usually due to direct contact with organic liquids but sometimes through absorption of vapours.

Assessing skin exposure isn’t easy. There are well established methods for estimating exposure to most common industrial chemicals by inhalation but there are a number of major difficulties involved in developing a good method for measuring uptake through the skin.

Starting in 2003, a major International conference has been held devoted to the science of skin exposure to chemicals at work and from the environment. BOHS hosted the fourth conference in Edinburgh two years ago. The latest conference was held in Toronto, Canada at the beginning of June. One of the keynote presentations was given by John Cherrie of the Institute of Occupational Medicine, and a former president of the BOHS. He provided a good summary of the current state of knowledge on skin exposure assessment. His presentation has just been posted on Slideshare and can be viewed below.

Image from jelaga @ stock.xchng

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Skin Exposure and COSHH Assessments

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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.

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Picture credits:

HSE Work-related skin disease image library

Preventing dermatitis at work. Advice for employers and employees

New NIOSH Skin Notations

I didn’t sit in on the session on the skin at the BOHS Conference in Harrogate. Unfortunately it clashed with some other presentations I wanted to see. That’s the trouble with parallel sessions. Sometimes, as on this occasion, there is more than one session I want to sit in on while on other occasions none of the sessions appeal.

During the skin session, John Cherrie of IOM gave a presentation on the new approach to skin notations adopted by NIOSH. Luckily, he’s posted his slides on Slideshare. Here they are.