29 January 2019

Lead in backyard eggs: Should we care?

I recently shared a Stuff article about lead in NZ backyard eggs on the Keeping Chickens NZ Facebook page. Since then I've read plenty and discussed the issue with some experts. I specifically wanted to find out for you:
(1) Is this worth being concerned about, or is it scaremongering?
(2) If you're concerned, what should you do?
(3) If your land has lead in it, can you still keep chickens and eat their eggs?

Are these all good?

Is Stuff full of stupid stuff?

A couple of FB-followers commented that they don't believe what they read on Stuff. In this case, at least, Stuff's report is valid: it's an accurate report of a paper that was published in December 2018 in the New Zealand Veterinary Journal. A summary of that study is here. It looks like a well-conducted, rigorous study.

Is lead anything to worry about?

One FB follower commented that they'd rather have backyard eggs with lead than eggs with antibiotics from stressed hens. I get that - I am a lover of things natural and homegrown. Our family's food comes as much as possible from our garden and the Farmer's Market. But if I had to choose, give me antibiotics over secretive, damaging lead any day.

Our outdoor pantry.

Our bodies need certain metals for good health - zinc and iron, for example - but lead is not a natural part of the human diet. It is an odourless, tasteless neurotoxin for which zero is the only safe level. It is never expelled from our bodies but simply accumulates. It does not biodegrade. There is an overwhelming amount of evidence that it damages brains and lowers intelligence.

Just last week a new study was released showing an association between high blood levels at age 11 and psychopathology in adulthood. The results came from nearly 600 people who were children in Dunedin in the 1970s.

There's information here from the World Health Organisation on the problem.

But lead is a fact of modern life, and below a certain level of it in our bodies (which is not zero), we seem to be okay. We cannot completely escape the lead that our predecessors put into our environment, not realising that it was harmful, so we'll all have some inside us. We just need to minimize it.

If we have babies and children, it's worth being more paranoid: they tend to ingest more of it and their developing brains are more vulnerable. The effects are thought to be irreversible. So, in my opinion, if you're a parent of little ones, it's not really your "personal choice" whether you care about lead.

However, to put things in context, since New Zealand has tackled the lead problem, modern-day children have a lot less lead in their blood than they did in the 1970s when I was born (although who wouldn't like a few more IQ points ...)



Our family's earliest days of chicken-keeping.


What the study showed

The NZ Vet Journal study showed that all the eggs in their study contained lead. Over half of them had a higher-than-safe level of lead. They also took blood samples from the chickens which, as you can imagine, had similar levels of lead as were found in their eggs.

It's worth noting that this study was conducted in backyard eggs from central Auckland, which is an area with plenty of old weatherboard houses that were likely to have been painted with lead paint. But there are plenty of those all over the country.

The study concluded that higher lead levels came from chickens living outside houses that were:
1) Clad with weatherboard;
2) Built before 1940.

Where lead comes from: paint, petrol, pesticides

We've all seen our chickens gobble cockroaches and worms covered in dirt. Yum. But chickens get lead from the soil in which they forage, and from the invertebrates they eat that live in that soil.

Chickens eat dirty stuff - much dirtier than this.

Sometimes there is lead in that soil, resting there from historical contamination. There is no way to detect it without lab tests, but there are some clues that lead might be there. Before we hand over money to lead-testers, I wanted to find out how each of us can figure out if we might have lead on our land.

I spoke to Dave Bull, a director of Hail Environmental. As we spoke, I realized that if there is anything about lead worth knowing, this guy knows it. And until he had to move house recently, he was a chicken keeper! Perfect. So, what did I learn?

Paint
NZ houses used to be painted with lead paint, and in some cases that persisted until the 1980s. Little ol' NZ was pretty slow to the international lead paint-banning party that was held to celebrate the realization of how toxic the stuff is. Dave reckons that if your house is not brick-clad and was built before 1950, it's very likely to have been painted with lead paint, and in the interim someone has probably sanded it and repainted. The sanding dust sunk into the soil and its lead will still be there.

I adore old houses. Except for the lead.
Most of it will probably be within two metres of your house - or your garage, if you have one of that era, as that was probably also painted with lead paint.

If your chickens are many metres away from your house and garage along your back fence boundary, there is probably less lead there.

Resene does free tests for lead paint - you can just take in a flake or board and give it to them. They can only tell what's on it now, of course.

Petrol
Obviously we have unleaded petrol these days, and by now you know what motivated the 1987 change to unleaded petrol. Exhaust emissions used to contain lead.

If you live on a road that was a busy traffic road before the 1990s, your front yard probably has lead in it. Happily, that lead doesn't spread far, so although it would be a bad idea to keep chooks at the front of your house, the backyard is likely to be unaffected. Dave says that the land within eight metres of the road is the bit to avoid.

Pesticides
I hate the passion-vine hoppers sucking the life out of our citrus and beans! Insect pests have been a problem for a long time, and many of our parents, grandparents and great-grandparents sprayed them, especially if they were growing crops for a living. A commonly-used spray was lead arsenate. Apparently it was brilliant at controlling all sorts of insects: grass grub, codling moth in apples, and aphids on roses. But it left lead (and arsenic) in the soil.

The ever-present annoyance of insect pests.
It's impossible to know how people gardened on your property in the past, which is a worry. But if your land used to be orchard land or market gardens - and several towns in New Zealand have expanded their housing over old horticultural land - it might be worth testing for lead.

Old industry
There are some industrial land uses that have left a legacy of high lead levels in soil. There was once a battery factory in Onehunga, for example, that has left behind lead to within 100 to 300 metres of its site.

But what about lead in commercial eggs?

Commercial eggs have been tested for lead, and the lead was below detectable levels, which is much more desirable than the studied Auckland backyard eggs. This result is from a 2016 Ministry of Primary Industries "New Zealand Total Diet Study" (see page 173 - I'm guessing these are battery cage eggs, not free range).

How do I find out if our eggs have lead?

Firstly, unless your chickens have very high lead levels, they may still appear healthy - but the levels can still be worryingly high.

If you have an old house, or keep your chickens close to a busy road, or live on old horticultural land, or have young children, it might be worth having some testing done.

You have two options:
1. Take at least one of your hens to a vet and ask for a blood test for lead. I've been told by a lovely vet at Cambridge Vets that the test will cost $100 plus the consultation fee to take the blood. She advised that a trip to the vet and the blood sampling is likely to be stressful to your hens, and more expensive than the next option:
2. Send an egg or eggs to Hill Laboratories in Hamilton (confession: my husband works there, although not in the food section! But this recommendation comes from the study author. I am not even sure there's another commercial lab in the country that can do it).

At Hill Labs, the cost is $66+GST per analysis. You can ask for that to be an analysis of one egg, or you can ask them to mix together the content of several eggs (three would provide a good average) and do one analysis on that combination. You can also ask for each egg to be analysed individually, in which case each egg will cost you the $66+GST. Just be very clear in your instructions, they tell me!
Package the eggs very carefully so they won't break when you send them. To encourage the courier to treat eggs as fragile, write FRAGILE! EGGS! on the package. You'll need to accompany your eggs with a filled-out version of this form. Contact them with any questions.

How high is too high?

In eggs, if the result is more than 0.1 mg/kg of lead, it's too high. The paper authors say that:
"There is no maximum permissible level for lead in eggs in New Zealand ... the Ministry for Primary Industries advises that lead concentrations in eggs should be ‘as low as reasonably achievable’. In the edible portion of eggs, this is a target of 0.002 mg/kg or less, based on the 2009 New Zealand Total Diet Study ... ". In the NZ Vet Journal study, all the eggs had more lead than that! Instead, they treated the maximum level as 0.1 mg/kg, which is the maximum permissible level for lead in meat, according to the Ministry for Primary Industries.

What if our eggs do have a high level of lead?

This is the toughest question to answer. I'd be talking to the people at Hill Labs about having soil testing done. Contaminants such as lead tend to be patchily distributed, and there may be low-lead parts of your property that are better suited for chicken-keeping. At that point you would probably need to get new chickens, because lead will have built up in the old ones (although see the comments from Lena, below).

If your whole property contains lead, here are some recommendations for reducing lead uptake:
- keeping new chickens away from soil on paved surfaces (you could add straw), possibly elevating the coop;
- not allowing them to free range where they can access soil and invertebrates;
- keeping them on grassed areas with no bare soil (they'd still get contaminated invertebrates, though);
- never feeding them their eggshells (buy oyster-shell grit for them instead) - and don't compost the eggshells;
- provide uncontaminated soil, ash or sand for them to dust-bathe in.

Dave Bull of Hail Environmental is a consultant who can help you figure out anything you want to know about contamination with lead or other substances, including just how worried you should be. He tells me he spends quite a lot of time telling people that the problem isn't as bad as they think.

One follower of the Keeping Chickens NZ Facebook page found out her chickens had high levels of lead, as did her soil, and shared this excellent information about her experience:

"The problem then was that I could treat them - you can inject a solution that binds lead and encourages them to excrete it from their bodies - but as soon as you got their levels down - which you can do in some cases if their load's not too high - they would reingest lead from our contaminated soil. I loved those little lasses (they were ex-battery so they'd had a tough life already) so I went as far as researching how to remediate soil. I put down matting in an area that covered their coop and run and got fresh topsoil (one garden supplies shop was able to supply guaranteed clean topsoil from a farm in the Far North). My plan was to try and rehome them but one died from egg peritonitis some months later and the second's levels kept going up (possibly from eating worms or other dirt-dwellers around the coop area).

"And then the saddest part - they excrete the lead, so their pee and poo recontaminates, or contaminates other areas."

You can read the rest of her helpful comments underneath the original Facebook page post.
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Thank you to all the experts who helped me gather this information: Professor Brett Gartrell (Massey University), Graham Corban (Hill Laboratories), Dave Bull (Hail Environmental) and Cecilia van Velsen (Cambridge Vets).

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