Case study 4: Doctor, my guts...

This story is based on real events. They happen relatively rarely but they keep on happening time and again, all over the world. You may encounter something like this once or twice in your professional life. Will you miss it?

A 20-year-old man, unemployed for over a year, is told by his older brother that the firm he works for is looking for new men. It is a construction job, the project being to refurbish a main line railway station in the area. Our 20 year old has previously worked in construction and he applies and gets the job, which involves the removal of old paintwork off all metal structures in the station area and then repainting. Much of the paint is removed by physical means using hand-held needle guns and chisel hammers but some is also 'burnt off'. He is given minimal training, as he is already familiar with the tools. On his first day on site he is shown the canteen portacabin and the washing facilities, showers and toilets.

Approximately two months after starting his new job our construction worker starts to feel tired, lethargic and irritable with vague but generalised abdominal pains and the occasional loose stools. He visits his GP who examines his abdomen, finds nothing untoward and explains that he possibly has a viral infection. Another week later he revisits his GP now with increased abdominal pain and tenderness. His GP rushes him into hospital from the surgery.

Within hours of admission his condition has deteriorated and though he remains apyrexial and all the usual blood tests results are normal, except for a slight normocytic, normochromic anaemia of 11g/dl, he still has generalised and severe abdominal pain with marked guarding. He is taken to theatre and undergoes an emergency laparotomy. To everyone's surprise nothing abnormal is found.

His brother and family visit him on the ward that evening. "Didn't you get a blood test at work?", asks the brother.

• What blood tests and why?
• An unnecessary surgical procedure has been carried out. What questions should have been asked to identify this man’s gut pain with respect to the work he has done?
• Is there an official system for checking the workplace?

All his symptoms are consistent with acute lead poisoning. Abdominal pain, moderate-to-severe, usually diffuse, vomiting, encephalopathy, jaundice (due to hepatitis), lethargy (due to haemolytic anaemia). Lead poisoning can cause neuro-, renal- and hepatic-toxicity.

An old saying in occupational medicine is that if you don’t know the answer just say "it's lead poisoning". This is because the presence of lead in our environment is ubiquitous and it keeps popping up unexpectedly. Also it can produce a wide variety of different symptoms of which this case is the most common and typical.

Although the toxic effects of lead have been known for centuries, from the 1960s onwards lead was increasingly recognised as a public health hazard - from leaded fuel and from domestic leaded paint - in addition to its long-established effect on occupational health. Lead poisoning by inhalation (including smoking items with lead contamination); ingestion (lead contamination of drinking water, canned foods and hands handling food); or even through the skin (with lead alkyls) remains a serious problem for some groups of children and adults. Adults are primarily exposed in the workplace. "Take home" lead exposure, resulting from lead particles brought home on a worker’s clothes, shoes or body, can also poison other household members, with children being particularly vulnerable.

Construction has long been recognised as a high hazard/high risk industry which is also hard to 'police' from a health and safety point of view since site conditions often change from day to day, and workers move from site to site. Lead is a recognised chemical hazard in 2 areas of this sector's activities, namely demolition and refurbishment. The paints on many structures, including railway bridges and stations, road furniture and road bridges, contain a lot of lead - 50% by weight is not uncommon in old and weathered primer. During renovation, tasks such as abrasive blasting (dry or wet shot blast), hand chipping or with powered needle guns, welding, and torch cutting of surfaces coated with lead-based paints have high risk of lead exposure due to the generation of lead dusts and fumes. Without appropriate control measures in place these construction workers face the potential for significant lead exposure and even ill health. When the OSHA standard to control lead exposure was introduced in the USA in 1978, construction workers were specifically exempted from some of the requirements on various grounds, including brief and variable exposure and difficulties of provision. Exposure monitoring, provision of hygiene facilities and medical surveillance were not required for construction workers in the USA until 1993 at the same time as the lead in air limit was changed from 200 µg/m3 to 50 µg/m3. This followed a NIOSH alert calling for assistance in preventing lead poisoning of workers engaged in maintenance, repainting or demolition of bridges and other steel structures coated with leaded paint. Levin et al (1997) reported the improvement in workers’ blood lead on a major bridge renovation project in 1993-4 during the transition to implementation of the more stringent OSHA Standard.

(OSHA is the U.S. Occupational Safety and Health Administration, similar in a lot of ways to the UK Health and Safety Executive - HSE). (NIOSH is the U.S. National Institute of Safety and Health and its job is to challenge and research work risks. It hasn't got a direct UK equivalent but HSE does quite a lot of the same sort of work).

What follows now is rather detailed science which just gives and insight into the sort of subtle and careful research which may be needed to properly evaluate occupational health issues. There is a tendency to think these things are simple and obvious. Often they are not. Here we have taken a look at some recent studies into various aspects of lead exposure, protection and absorption in lead exposed US construction workers.

There is a tendency to assume that the most exposed workers will present with the highest blood leads and that the main route of absorption is inhalation. This seemed to be supported by Feldman's study, which divided workers into oxygas "burners" and "non-burners" and found that the blood leads in the non-burners were significant but lower than those of the burners. However, neither assumption is true, IF the most exposed workers are given protection but the hygiene system in place does not protect everybody equally. Piacitelli, reporting on a bridge renovation site in Connecticut, identified other significant routes of absorption and commented on the risks of taking contamination home on body and clothing through not washing and changing before leaving site. The authors identified the highest levels of contamination in workers’ automobiles for a low-exposure group (industrial hygienist/safety officers) and the lowest contamination for a high-exposure group (blasters and painters). They related this to the observation that only 25% of the low-exposure group wore company-supplied clothing and changed, or showered and changed before going home. Half of this group took their work shoes home. By contrast, 90% of the high-exposure group wore company clothing and changed, or showered and changed before going home. None took their work footwear home. Results to the same effect were obtained at a bridge site in Ohio. A substantial NIOSH publication made extensive recommendations about these matters.

Two other studies identified lead poisoning in workers doing concrete breaking and renovation on a bridge that had supposedly had the leaded paint removed some years previously. There were few protective arrangements in place (no respiratory protective equipment or engineering controls, no requirement to change clothes or wash or shower). After provision of information, equipment and training to the workers and improved hygiene arrangements, blood lead levels dropped significantly. The authors concluded that lead debris and residues could persist in inaccessible locations. The fact that workers doing work which is not particularly dust-raising may nevertheless have high lead absorption has been reported a number of times.

In Great Britain, control of lead at work is 'managed', to an extent, by statutory legislation. The Control of Lead at Work Regulations (CLAW) 2002 (revised version of the original 1980 legislation) places a duty on the employer to identify lead in the workplace and assess whether exposure is likely to be significant either by inhalation, ingestion or through the skin. Where workers are significantly exposed the law then requires statutory medical surveillance to include biological monitoring; such statutory surveillance must be carried out by a Health and Safety Executive (HSE) Medical Inspector or an Appointed Doctor appointed by the HSE.

• Vork KL, Hammond SK, Sparer J, Cullen MR. Prevention of lead poisoning in construction: a new public health approach. Am J Ind Med 2001; 39: 243-253.
• Health and Safety Executive. Control of Lead at Work Regulations 2002. Approved code of practice and guidance. HSE.
• Centres for Disease Control and Prevention. Screening young children for lead poisoning: Guidance for state and local public health officials. US Department of Health and Human Services, Public Health Service, Atlanta: 1997.
• Whelan EA, Piacitelli GM et al. Elevated blood lead levels in children of construction workers. Am J of Pub Health 1997; 87(8): 1352-1355.