Lead levels in air

Why we monitor lead levels in air

Lead is a heavy metal that can affect people’s:

nervous system – for example, causing headaches, disturbed sleep, depression, difficulty concentrating
immune system – decreasing the body’s ability to fight infection
blood pressure – causing it to increase.

Children are more at risk from lead poisoning than adults. Lead is dangerous to children because it can cause brain damage, affect their growth, and cause learning and behavioural problems. Young children can swallow harmful amounts of lead by eating, chewing or putting lead contaminated paint flakes or dust in their mouths.

Motor vehicle emissions used to be a major source of lead in Hamilton. In the mid-1980s steps were put in place by the New Zealand Government to reduce the amount of lead in fuels. Lead was later removed from fuels in 1996. This has eliminated a major source of lead in the environment. The removal of lead from fuels indicates that reductions in lead are likely in all areas of the Waikato Region.

Removal of lead-based paint from houses can still cause lead poisoning. Although it’s not used for exterior house paint in New Zealand anymore, lead-based paint can still be found on some older houses (especially those built before the late 1970s). Young children can swallow harmful amounts of lead by eating, chewing or putting lead-contaminated paint flakes or dust in their mouths. Pets are also susceptible to lead poisoning.

Another, localised source of lead in the environment is from old lead-based paint. Although it’s not used for exterior house paint in New Zealand anymore, lead-based paint can still be found on some older houses (especially those built before the late 1970s).

Lead from paint can enter the environment as:

dust - for example, when old paint is being removed
flakes - from old, deteriorating flaky paint.

Find out more about lead from the Occupational Safety and Health Service (OSH).

Waikato Regional Council measured ambient air lead levels in Hamilton. Hamilton was suspected to be at risk from lead because of high levels of traffic.

What's happening?

Lead was measured in Hamilton from 1983 to 2001. Results show a large drop in the amount of lead in Hamilton’s air. From August 1993 to August 2001, lead levels were consistently below the Ministry for the Environment guideline value (0.2 µg/m³ as a three-monthly average), indicating that lead is no longer of concern in Hamilton.

Methods - how we monitor

Lead was monitored in Hamilton at Waikato Regional Council's Whitiora Road monitoring site from August 1983 to August 2001.
Lead concentrations were measured continuously on a seven-day average measurement. Data were reported as a three-month moving averages.
Lead monitoring started at Waikato Regional Council's Whitiora Road monitoring site in August 1983 and finished in August 2001. Some periods of missing data did occur. The largest of these were:
- July 2 to October 31, 1984
- November 2, 1993 to June 30, 1994
- May 2 to June 30, 1995
- June 2 to September 30, 1999
- March 2 to June 30, 2000.
Total suspended particulate (TSP) concentrations were measured using high volume gravimetric (continuous) sampling over a seven-day period. The lead content of the particulate was then measured, and averaged monthly, by the WaterCare Services Laboratory in Auckland.
Monitoring results are reported in relation to the Waikato Regional Plan, using the Ministry for the Environment (2002) guideline of 0.2 µg/m³ for lead.
Lead monitoring was carried out in Hamilton only. However, the removal of lead from petrol indicates that reductions in lead are likely in all areas of the Waikato Region.