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Lead exposure linked to cataracts

Discussion in 'Handloading and Reloading' started by Preacherman, Feb 10, 2005.

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  1. Preacherman

    Preacherman Member

    Dec 20, 2002
    Louisiana, USA
    The following article was posted on the API List by a member who commented that it might explain why he has a beginning cataract at age 51. He commented: "Years of being a commercial reloader coming back to haunt me, I reckon".

    From Health And Age (http://www.healthandage.com/Home/!gm=20!gc=41!gid2=2953!gnews=01100205):

    Lead and Cataracts?

    Summarized by Robert W. Griffith, MD
    January 21, 2005


    Lead is a toxic substance that can enter the body in a number of ways - inhalation of lead dust (paint) or fumes (gasoline), or through the gastrointestinal tract (contaminated hands, food, or water). Once in the body, lead is distributed by the blood to all parts, but more than 90% of the total body lead is accumulated in the bones. From here it can be released into the blood again, re-exposing organs long after the original exposure.

    Numerous organs and tissues are affected by lead, to varying degrees. Common lead toxicities are: neuropathy (nerve damage), seizures, fatigue, nausea, vomiting, constipation, miscarriage, infertility, anemia, and kidney damage. Now a new organ must be added to the list: the cornea. A recent publication has reported a link between bone lead levels and the occurrence of cataracts in older men. It's published in the Journal of the American Medical Association, and summarized here.

    What was done

    Fortunately the bone lead levels can be measured by a type of radiography: K x-ray fluorescence. Levels in the tibia (lower leg bone) and patella (knee-cap) were measured in 642 men over 60 who were taking part in the Normative Aging Study (NAS) running in Boston, Massachusetts. All participants in the NAS had full physical exams every 3 to 5 years that included an extensive eye exam.

    The subjects were classified into 5 groups (called quintiles) according to their tibia lead levels. This allowed analysis for a link between high lead levels and the presence of cataracts.

    What was found

    The average age of the subjects was 69. The concentration of lead in the tibia ranged from 0 to 126 microgram/gram of bone, and in the patella from 0 to 165 microgram/gram. Blood levels ranged from 0 to 35 microgram/dL. Higher bone lead levels were found in those who were older, smoked more, and had diabetes.

    There were 122 cases of cataract among the 622 men. After adjusting for the possible effect of age, the men in the highest lead level quintile were 2.7 times as likely to have a cataract as those in the lowest quintile.

    After further adjustments for possible effects of smoking, diabetes, and vitamin C or carotenoid intake (which can influence blood lead levels), the highest quintile group were 3.2 times as likely to have a cataract as those in the lowest quintile.

    Finding for the patella lead levels were similar. Blood lead levels were not significantly associated with cataract; this was not surprising, as they are more likely to reflect short-term lead exposure.

    What this means

    Over 80% of home built in the USA before 1980 are contaminated with lead-based paint or leaded water pipes. It's not surprising that most US adults have accumulated a substantial amount of lead in their bones. This present study suggests that cumulative lead exposure is a risk factor for cataract, a condition responsible for 40% of the cases of blindness worldwide.

    The investigators propose several ways that lead can promote the development of cataract. First, the metal can upset the electric potential in the lens that's necessary to maintain lens clarity. Alternatively, lead may interrupt the metabolism in the lens of two substances, glutathione and malondialdehyde, allowing one or both to accumulate there. Finally, lead can interfere with calcium levels in tissues, and this may occur in the lens.

    As we age, the likelihood of needing cataract surgery increases. About 1.5 million cataract surgeries are done each year in the USA, and their cost is the largest single item in the Medicare budget. Approximately 10 million cateract surgeries are done in the entire world each year. The cataract burden is greater in many developing countries, and that's where lead exposure continues to be high. It would be a wonderful thing if ongoing global reduction of lead exposure resulted in decreased cataracts around the world.

    Source: Accumulated lead exposure and risk of age-related cataract in men. DA. Schaumberg, F. Mendes, M. Balaram, et al., JAMA, 2004, vol. 292, pp. 2750--2754
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