4 Feb 2021

The Toxicology of Lead - Your Questions Answered

From Nights, 7:35 pm on 4 February 2021

It wasn't in the schedule to talk to our regular toxicologist Leo Schep, but considering the news from North Dunedin, we though we'd get him on for a refresher on the toxicology of lead.

A water tanker near the Golden Fleece Hotel in Waikouaiti where high lead levels were discovered in the water supply.

Photo: RNZ / Tess Brunton

Q. Hi, I have a question for Leo please. Every household in Karitāne has to store their water in a tank as we have an unusual trickle feed supply. Does this mean the lead is in our tanks, does it float around in the water or does it sink to the bottom of the tank and is lurking there in high concentrations? I'm really worried about this as the outlet of our tanks is of course at the bottom of the tanks. This issue of the tanks has not been raised in the media at all.

A. The lead that is in the water will remain dissolved in the water and should not either float to the top or sink to the bottom. You had best discuss with the DCC or Otago Regional Council whether you need to discard this water or not

Q. Hi Brian - please could you ask your scientist about formula fed babies who have formula made with boiled tap water from the lead contaminated local supply?

A. Boiling the water will only increase the concertation of lead in the water. Best use water provided by water tankers to make up your formula

Q. Ask him about the difference between adults and children in lead effects

A. Children are more susceptible to lead poisoning that adults

Q. How accurate are blood tests if it's absorbed into bone and not circulating

A. Measurement of bone concentration is a better measure of the total body burden of lead that reflects long-term exposure to lead. In contrast, blood concentration is more a reflection of recent exposure to lead.

Q. Zero point zero one is the same as zero point zero ten. And please have your guest clarify the decimal points in a microgram

A. 10 micrograms per litre is the same as 0.01 mg/litre or, if you like, 0.010 mg/litre.

Q. Please can the esteemed toxicologist tell us whether lead on the water is transferred to an infant on breast milk

A. Lead will transfer to breast milk. Investigations suggest human breast milk concentrations range from 0.6 to 3% of maternal blood lead. If the person texting this message is breast feeding, they need to discus this further with their health care provider.

Q. As a resident of Karitane I am exceptionally concerned for both my health, and my young children's health. At such a high amount (40x the limit) is there anything we can do to minimise any effect that the lead is doing

A. Blood testing will be available next week and this will help determine the risk of toxicity. You should be able to get advice on what needs to be done then and if there are any further concerns, you can call the National Poisons Centre for further advice.

Q. Blood test the 'gold standard for recent exposure only, surely. Blood cells are short lived. For past exposure it would be hair, wouldn't it?

A Of course blood cells are short living, but they do circulate in the body for up to 100 to 120 days. That gives a sufficient window of opportunity to determine concentrations following recent exposure. Re hair test, that is another option (hair grows at ~ 1cm/month, so if your hair is 10 cm long, this can roughly correlate to ~ 10 months of potential exposure to lead) but first discuss this with your health care provider on companies within New Zealand that have the appropriate certification to conduct these tests.

Re transfer of lead to the unborn child. In pregnant patients there may be a risk of adverse effects in the unborn child in elevated maternal blood lead concentrations