In the Dec/06 issue of (US) Environmental Health Perspectives, a group of US doctors & environmental health practitioners published 5 papers, a "mini-monograph" arguing that there is an urgent need for significant reductions in occupational exposure limits for lead around the world. They claim that whereas current occupational standards focus mainly on issues related to high-level exposures, modern concerns relate rather to low level chronic exposures (eg cognitive ability, blood pressure, reproductive ability). They also believe that it is not just the blood lead level at any particular moment in time that matters, but also the cumulative dose of lead over a working lifetime. Moreover, they believe there are sub-groups of the population with particular susceptibility to lead, & that exposure standards should be set to protect the most susceptible workers. While the authors believe that bone lead levels or a cumulative blood lead index would constitute good measures of exposure, they recognise the limitations of both approaches and therefore present recommendations for occupational exposure limits based on conventional blood lead levels. To prevent acute effects of recent dose they recommend that blood lead levels should not exceed 20 µg/dl, whilst to avoid chronic health effects due to cumulative dose they recommend maintaining blood lead levels below 20 µg/dl for 10-20 years of exposure, or 10 µg/dl for 20 to 40 years of exposure. For pregnant women, it is recommended that blood lead levels should not exceed 5 µg/dl.
