Saturday, December 12, 2009

DNA Damage and Chromosomal Aberrations: Threats to Current and Future Generations

Environmental and human health concerns related to electronic waste were first raised by the international community more than a decade ago [1]. After noticing the rapidly expanding mountains of e-waste in places like Guiyu, in the Guangdong Province of China, governments have been persuaded to take action to alleviate the negative impacts of e-waste. For example, in Jinghai County of Tianjin, in Northern China, the local government has built an "environmental protection industry park" to minimize environmental pollution [2]; however, researchers have noted that many residents have not been using the park in order to reduce costs [3]. The manual disassembly and illegal burning of e-waste continues to occur [4]. These primitive practices not only create an enormous amount of environmental pollution, but also disseminate genotoxic agents that threaten the health of current and future generations living in the local environment.

What are Genotoxins?
Genotoxins are agents that damage the genetic material in cells. Furthermore, they are toxins that have been found to be mutagenic or carcinogenic, meaning they are capable of causing genetic mutations or the development of cancer [5]. The genotoxins associated with e-waste include: metals such as chromium, beryllium, and cadmium; chlorinated dioxins and furans formed from the burning of plastics; and, flame retardants such as polybrominated diphenyl ethers [6].

What is DNA damage? And a chromosomal aberration?
DNA damage is an umbrella term used to define all types of physical abnormalities in DNA. Typically, these abnormalities are detected and fixed by the body, and in fact are often occurring naturally in the body [3,7]. DNA damage is particularly problematic when it leads to DNA mutations: changes to the DNA sequence [8].

A chromosome is an organized structure of DNA; therefore, a chromosomal aberration is just a change in the normal structure or number of chromosomes within a cell [9].

Changes to a cell's
DNA or chromosomes can lead to a number of pathologies including genetic disorders, infertility, spontaneous abortions, elevated cancer risk and premature aging [3,5].

Does exposure to e-waste processing lead to DNA damage and chromosomal aberrations?
Three studies were found that looked at DNA damage associated with exposure to e-waste processing. One of the studies was already discussed in my post about polybrominated diphenyl ethers (PBDE) [10]. Of the remaining two, one measured DNA damage associated with chromium exposure from e-wastes [7], and the other focused on measuring elevations in risk of DNA damage and chromosomal aberrations attributable to e-wastes [3]. Measuring the damage to genetic information in cells holds great public health importance because it enables the investigation of toxicities that may accumulate in the human body over many years and essentially go undetected until pathologies develop. These markers can be used to emphasize the urgent need for public health interventions in order to mitigate exposure and potentially avoid serious health outcomes. Not only are there cumulative health risks for the current populations exposed, but with damages to the genetic information of these individuals there are also great healths risks for future generations (their offspring)[3].

All three studies did find an elevated risk of DNA damage; hence, the discovery that exposure to e-waste pollutants produced by the dumping and recycling of e-wastes may be mutagenic. The PBDE study estimated that the odds of developing genetic damage after having a history of working with e-waste in village in southeast China was 38.85 times the odds for someone of similar characteristics, who didn't have a history of working with e-waste (range, 1.11 to 1358.71; p=0.044)
[10]. Similarly, in the study looking at chromium exposure, umbilical cord blood chromium levels (UCBCL) in neonates was significantly positively correlated with the time their mothers spent roaming in e-waste recycling sites during pregnancy. Furthermore, UCBCLs in neonates was discovered to have a significant positive correlation with DNA damage of lymphocytes (white blood cells) [7]. This confirms the hypothesized risk of DNA damage beginning early in the life of new generations, as a result of e-waste pollutants.

The third paper I found was exceptionally well done. Both the exposure and outcome was well measured, the methods were transparent and validated, and the author's suggestions were insightful and well supported. This study looked at multiple types of chromosomal aberrations and DNA damage. Their analysis detected a significant difference in DNA damage among the randomly selected permanent residents of three villages with numerous e-waste disposal sites (exposed, 171 villagers), compared to randomly selected permanent residents from neighbouring towns without any e-waste disposal sites (unexposed, 30 villagers). Additionally, the total chromosomal aberration rate in the exposed group was significantly higher than in the unexposed group (5.50% versus 0.28%, respectively; p<0.0001)[3].

Bottom Line
The unsafe handling and recycling of e-waste can lead to human exposure to genotoxic substances, which has been shown to lead to genetic damage. These findings are extremely worrisome, and
emphasize the need for stricter control measures to eliminate outdated recycling practices and the illegal importation of e-waste in order to protect current and future generations from the immediate and long-term effects of pollutants from e-waste. Fundamental changes are needed in the approach to e-waste management, and they need to come quickly.

3 comments:

  1. Good to see research on biological effect markers linked to exposure. Glad to see you bring out your critical appraisal hat and focus down on strengths and weaknesses, particularly the last study, with effect sizes, not just significance as per the abstract. I think you could also highlight the chain of exposure effects assessment e.g. location and activity, biological measure of contaminant exposure, biological measure of neonate health effects. Good to have bottom lines wrt prevention, but you could also suggest research directions.

    ReplyDelete
  2. EnvironmentCare.in(http://www.environmentcare.in/) is India's 1st environmental B2B portal.It is an online one stop go Green source to provide end to end solutions for environment protection, pollution control management, energy conservation, renewable energy, e-waste management and safety management.
    EnvironmentCare.in also provide live discussion, Blogs, Environment friendly calculator, Games with Learn and much more interesting and educational section.
    You can follow us on http://www.facebook.com/environmentcare.in, http://www.linkedin.com/in/environmentcare and https://twitter.com/B2B_Portal.

    ReplyDelete
  3. Hello,Great post! Thanks you so much for the share. It is indeed a helpful one. I am looking forward of reading more article with the similar topic as this one. Good luck and More Power.
    e waste recycling companies

    ReplyDelete