The dangers of lead

Lead is a potent neurotoxin with no known safe exposure level; there is no way to soften the harsh reality of that.

Exposure to even very small amounts in utero and in childhood can cause brain damage in children, leading to loss of function, decreased IQ scores and behavioural problems including attention-deficit hyperactivity disorder (ADHD).  Children are at greater risk of lead toxicity than adults as they are more likely to put objects in their mouth (including those that contain lead paint), they absorb a greater proportion of the lead compared to adults and they appear to deposit more in their brains and less in their bones compared to adults.

Less well known is the link between lead and hypertension and heart disease with even low-level exposure being also responsible for many cardiovascular deaths annually.  In many countries, Australia included, the levels have been steadily decreasing due to ending the use of lead-based petrol and paints.  In developing nations however, it remains a significant threat with 98% of adults and 99% of children affected by exposure to lead live in low- and middle-income countries.  In developed nations, those in older housing with lead-based paint are still at risk. 

Sources of lead

• Paints (in old unrenovated houses, and it is still in some paints for non-domestic use, eg art pigments)
• Ceramics
• Solder
• Soil, dolomite in the home garden and vege patch (esp under guttering drip line in old houses)
• Newsprint
• Pewter ware
• Ammunition
• Batteries
• Stained glass and crystal glassware
• Make-up, hair colouring
• Old toys
• Lead pencils!
• Old lead pipes or pipes joined by lead containing solders provide a source of lead.

How are you exposed and how is lead absorbed?

For the majority of people suffering lead toxicity it is due to prolonged and repeated exposure to lead, not a one-off exposure.  Exposure to lead can occur by:

1. Ingestion (with food or drink)
2. Inhalation
3. Skin contact

Whether you swallow, inhale or touch the lead, it is then absorbed into blood where nearly all of the iron binds to red blood cells (98–99%) with the rest being in the extracellular fluid (the fluid your cells swish about in).  The iron then crosses cell membranes and enters cells and then accumulates in soft (e.g. organs) and hard tissues (e.g. bones).  GIT absorption is the most common route of lead exposure and the gastrointestinal absorption of lead is much higher for children (30–50%) than for adults (5–10%).

Storage and excretion of lead 

Lead is a lingerer and can stay in the body long-term.  Absorbed lead is mainly excreted in the urine, via the kidneys, whereas lead that is ingested but not absorbed can be found in the faeces.

In children only up to about 70% if lead is stored in bones and teeth, whereas in adults up to 94% is stored in bones and teeth, which accounts for some of the more serious health effects on children.  In adults, that lead may stay stored in bones for decades!

Lead follows the movement of calcium in the body to a large extent, and changes and stresses in the body that effect calcium metabolism effect lead in a similar way.  When there is increased bone turnover, such as occurs in pregnancy, lactation, osteoporosis and other conditions, lead is released from the bones. Likewise, when the calcium deposits in the bones, lead will as well!

What protects you from absorbing lead

The amount of lead absorbed from the GIT can vary depending of the environment of the GIT, the health of the GIT wall, age and the nutritional status of the person. A well-nourished and healthy adult may absorb as little as 1% of ingested lead, and this is because some nutrients appear to reduce lead absorption as well as having a healthy GIT.  You absorb more iron on an empty stomach, so make sure you and your children have regular meals.  The following nutrients reduce lead absorption, thus being under-nourished increases the risk of absorption and toxicity:

• Vitamin C
• Vitamin E
• Calcium
• Iron
• and, to a lesser degree, zinc and phosphorus.

Vitamin D and folate (vitamin B9) can increase lead absorption, but that is offset by their positives: vitamin D can help decrease the quantity of lead stored in the bone, and folate appears to increases excretion more than it increases absorption.

What helps to excrete lead?

Having healthy kidneys!  In addition to that, two B vitamins play a key role in excreting lead, and both are mandated additives to non-organic bread in Australia.

• Vitamin B1 (thiamine) which specifically increases excretion of lead from the brain
• Vitamin B9 (folate or folic acid).

Other nutrients may also be helpful.  Vitamin B6 may also aid excretion but there is less research on this nutrient.  Vitamin C can chelate (bind) iron and help with excretion, but the research is a little inconsistent on the chelating effect of vitamin C and pectin may also be helpful.

Safe limits of lead

There is no safe level of lead.  In Australia it is recommended that if a person (especially a pregnant women or infant) has a blood lead levels of ≥5 µg/dL (0.24µmol/L) that an investigation of the source of lead be undertaken and that source be removed or the exposure reduced however possible.  Workplace levels are discussed below.

Signs and symptoms of lead toxicity

Lead effects all body systems (nervous, cardiovascular, endocrine, reproductive, immune, skin, respiratory and blood) but the key area of concern is the brain where lead cross the blood-brain barrier.  Negative impacts occur even at tiny doses, especially in the foetus, infants and children.  Brain and nervous system and behavioural problems include:

• Delayed mental development and permanent learning disabilities, poor concentration, poor short-term memory, reduced performance on visual intelligence and visual motor coordination tests.
• Seizures, coma
• Anxiety, irritability, hyperactivity
• Decreased nerve conduction (motor neuron disorders)
• Headaches

Other symptoms of lead toxicity include:

• Anaemia
• Fatigue
• Insomnia
• Metallic taste
• Loss of appetite, weight loss
• Abdominal pain, constipation
• Tingling in the hands and feet

Effects on fertility and reproduction

Lead negatively affects both the male and female reproduction.  In men, blood lead levels of 40 μg/dL or more causes a reduction in sperm count, reduces their ability to move normally (their motility) and can cause damaged and malformed sperm (abnormal morphology): all of these reduce male fertility and increase the risk of miscarriage in the woman. In addition, lead interferes with normal reproductive hormone secretion and function.

A pregnant woman with elevated blood lead levels has an increased risk of miscarriage or prematurity birth, low birth weight, and developmental problems of the child.  Just as lead can pass through the blood-brain barrier, it can also pass through the placenta to the foetus and into breast milk; and this can be illustrated by the mother and baby having similar lead levels.  In pregnancy women often increase calcium movement out of their bones and into their blood which is transferred to the foetus and lead follows the calcium so this is an additional risk during pregnancy and adequate calcium intake is critical.

What you can do to protect yourself and your family

At work

Be aware of your occupational exposure, risks and rights.  State governments have regulations about maximum safe levels and the levels for NSW state that “lead risk work” means work carried out in a lead process that is likely to cause the blood lead level of a worker carrying out the work to exceed:

At home

• Have a health, balanced diet with loads of variety and fresh foods (see nutrients above).
• Safely remove lead paints and restore or throw out old toys and glassware that contain lead.  The Environmental Protection Agency has some tips on the safe removal of lead paint here.
• NSW Health has an extensive guideline about how to manage different blood lead levels in different age groups and in pregnant women which can be found here.
• Test the soils in your garden!  Vegesafe is a fantastic, free service provided by Macquarie University where they will test your garden soil for you and provide guidelines for improving the soil and protecting your family; check it our here.  ABC TV’s Gardening Australia show also has information on keeing your soil safe, especially if growing veges in it!.
• Be careful about buying imported herbal medicines. In particular, loose leaf herbs from China and India have been found to contain level and other heavy metals and toxins.  I recommend buying Australian products as they are required to meet stringent TGA standards and they are safe.

 

Some resources

• World Health Organization.  2009.  Global health risks: mortality and burden of disease attributable to selected major risks.
• “Lead poisoning and health”. WHO. September 2016. Retrieved 14 October 2016.
• http://www.who.int/mediacentre/factsheets/fs379/en/
• http://www.epa.nsw.gov.au/pesticides/lead-safety.htm
• http://www.lead.org.au/lanv14n1/lanv14n1-16.html
• https://www.lead.org.au/fs/Fact_sheet-Nutrients_that_reduce_lead_poisoning_June_2010.pdf