We’ve long known that there is some association between lead exposure and hearing function (peripheral and central) in adults. The effects of heavy metals on adult hearing as a result of workplace exposure have been studied fairly extensively.  An up to date review of 49 studies was published last year (Castallanos & Fuente, 2016). Less is known about the effect of heavy metal exposure on children’s peripheral and central auditory function.

 

http://www.sacbee.com/news/local/health-and-medicine/article71355742.htmlAdolescent Hearing and Lead Exposure

 

A 2011 study by from Massachusetts Eye and Ear Infirmary indicates that “teens exposed to higher-than-normal levels of lead are more likely to have trouble hearing.”  A review of the study has a headline designed to alarm:  High Lead Exposure Linked to Hearing Loss in Youth.

But don’t be alarmed. Just register the already-known fact that you want to keep your kids (and yourself) clear of lead exposure. Here’s a more sedate, albeit sobering, take on the study findings:

Good News

  • Only 1 in 20 adolescents had high lead concentrations (2 mcg/dL or higher) that might be linked to hearing loss.
  • Lead levels are lower overall than they were several decades ago.
Bad News
  • Almost one third of the adolescents with those high levels of lead had some degree of hearing loss (>15 dB threshold(s).
  • The current US  standard for acceptable blood level in children is < 10 mcg/dL, which is 5 times higher than the “high” level defined in this study.
This is a chicken-egg set of findings because the researchers cannot tell, after the fact, whether the hearing loss was present before the lead exposure or after. Hence, cause and effect are not established.
 
That doesn’t mean lead exposure is NOT the cause, just that the hearing loss can’t be definitely pinned on it. Indeed, the correlation suggests that eventually the connection will be made definitive, and that the connection will be at significantly lower blood levels of lead than the Centers for Disease Control (CDC) currently consider dangerous.
 
So, even though lead exposure is lower now than in the past, it’s well worth parents’ time to be aware that lead may be present in old paint in old houses, in some soils, and occasionally in water supplies.  There is no doubt that repeated exposure to high lead levels can produce horrifying results — check out John Grisham’s latest novel, The Litigators, if you really want to scare yourself.  Be especially careful of children’s jewelry and toys, both of which may contain high levels of lead depending on where they were produced.
 

Take Home for Audiologists

 
More research is needed to deterrmine adverse effects of heavy metals on hearing, in children and adults.  Though causal relationships are not definitive and not all heavy metals are implicated at present (e.g., manganese), this is an active area of research which deserves monitoring by professionals and consumers:  
 
“…audiologists and other hearing health care professionals should be aware of the possible auditory effects of heavy metals.” (Castellanos & Fuente, 2016)
 

References

 
  1. Castellanos M-J & Fuente A.  The Adverse Effects of Heavy Metals with and without Noise Exposure on the Human Peripheral and Central Auditory System: A Literature Review. Int J Environ Res Public Health. 2016 Dec; 13(12): 1223. Published online 2016 Dec 9. doi:  10.3390/ijerph13121223 PMCID: PMC5201364
  2.  Shargorodsky J et al.  Heavy metals exposure and hearing loss in US adolescents. Arch Otolaryngol Head Neck Surg. 2011 Dec;137(12):1183-9. doi: 10.1001/archoto.2011.202.
 

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