Autism and the Environment 101: Online Course 9

Is the Government Doing Enough to Safeguard the Population From Environmental Toxins?

There are steps the government could take to decrease risk:

    • Currently, chemicals are studied only one at a time. In reality, we are exposed to hundreds at a time, and these chemicals add up and interact with each other. This means that even a chemical at a low dose can have its toxic impact multiplied in the presence of some other chemicals.
      • We need to learn how to study what happens when chemicals interact.
      • We also need to know that safety levels established for individual chemicals may not apply in real-life situations due to these interactions.
  • For each chemical, a “safe” level is established, the amount of the chemical allowed for human exposure before that exposure becomes toxic. But now we know that at very low doses, chemicals can confuse our body’s signals (like hormones or neurotransmitters) even if they don’t cause cell death or death of the person. Right now there are no tests in chemical regulation procedures that take these low-level dangers into account.
  • Regulators need to make it a high priority to face this problem and figure out what to do about it.
  • Over 60,000 chemicals that were on the market before regulation of chemicals began have been allowed to remain on the market without testing.
  • In Europe, researchers are going back and testing these.
  • In the USA, we have not started to do this, but we need to do this type of testing too.
  • At present, there is no requirement to test chemicals for their impact on the extremely sensitive developing nervous system – these tests are optional and the manufacturers usually don’t do them. As a result, of the approximately 3,000 chemicals produced in the largest volumes, only 20-30 have been tested using the EPA’s developmental neurotoxicology protocol. Because of this, we do not have any information regarding the effects on the developing human body and brain from exposure to most chemicals, particularly low doses or in combinations.1
  • We need to make developmental neurotoxicology testing a high priority and not just optional.

1 Claudio L, Kwa WC, Russell AL, Wallinga D. Testing Methods for Developmental Neurotoxicity of Environmental Chemicals. Toxicol Appl Pharmacol 2000; 164(1):1-14.Abstract: Human brain development is slow and delicate, involving many unique, though interrelated, cellular events. The fetus and child are often more susceptible to chemical toxins that alter the structure and/or function of the brain, although susceptibility varies for individual neurotoxicants. Early exposure to neurotoxins has been implicated in neurological diseases and mental retardation. Pesticide exposures pose a particular concern since many are designed to be neurotoxic to pests and can also affect humans. Acknowledging the potential for vulnerability of the developing brain, EPA recently began to “call in” data on developmental neurotoxicity (DNT) from manufacturers of pesticides already registered and considered to be neurotoxic-around 140 pesticides. Chemicals are to be tested following the DNT testing guideline (OPPTS 870.6300). This paper assesses whether tests performed according to this guideline can effectively identify developmental neurotoxicants. We found the testing guideline deficient in several respects, including: It is not always triggered appropriately within the current tiered system for testing; It does not expose developing animals during all critical periods of vulnerability; It does not assess effects that may become evident later in life; It does not include methodology for consideration of pharmacokinetic variables; Methodology for assessment of neurobehavioral, neuropathological, and morphometry is highly variable; Testing of neurochemical changes is limited and not always required. We propose modifications to the EPA testing guideline that would improve its adequacy for assessing and predicting risks to infants and children. This paper emphasizes that deficiencies in the testing methodology for developmental neurotoxicants represent a significant gap and increase the uncertainty in the establishment of safe levels of exposure to developing individuals, (C) 2000 Academic Press.


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