Guidelines for the Management of Lead-Based Paint
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8 ENVIRONMENTAL SURVEILLANCE
8.1 Introduction
There are many forms of lead in the environment. However, the exposure to lead from paint is only significant in the following cases:
- Inhalation of lead-based paint dust and fume.
- Ingestion of lead-based paintwork.
- Ingestion of lead in house dust.
- Ingestion of lead in soil.
The following sections describe the acceptable and unacceptable concentrations of lead in air, paint, dust and soil. Methods of measurement and interpretation of results are also considered.
8.2 Lead in air (occupational exposures)
The New Zealand Workplace Exposure Standards (WES) published by the Department of Labour (2002) set guidelines for exposure (via inhalation) for hazardous substances in occupational settings.
The WES are not intended as a boundary between safe/dangerous exposures as individual susceptibility and pre-existing medical conditions can make a person more/ less susceptible at the same concentrations. As such the intention should not be to aim for 'just below' the WES but to keep airborne exposure as far below the WES as is practicable. It is good occupational health practice to take steps to reduce exposure when levels are more than 25% of the WES-TWA.
The WES that applies to lead from lead-based paint is the WES-Time Weighted Average (WES-TWA). The WES-TWA is designed to protect the worker from the effects of long term exposure to the substance.
Table 5: Airborne lead concentration
| WES-TWA (8-hour shift) | 0.1 mg/m3 |
| WES-TWA (12 hour shift) | 0.05 mg/m3 |
| Action level | 25% of WES-TWA |
It should be noted that:
- the WES-TWA applies to eight-hour exposure. If work shifts are longer than eight hours, the WES-TWA must be reduced to adjust for the longer period of exposure
- in all instances the WES relates to exposure that has been determined by personal exposure monitoring whereby a worker wears the monitoring equipment so that airborne lead levels in the breathing zone can be measured.
- these guidelines are designed for interpretation by persons in occupational health practice.
8.3 Lead in house dust
Lead in house dust comes from many possible sources, outdoor and indoors. The amount is thus dependent on a number of factors, such as the amount of painted wood present, property age, property condition, distance from a major road and residents' occupations and hobbies.
Once in the home, dust accumulations are affected by their location, surface texture and cleaning routines. Consequently it is not possible to state a single value for the 'normal' lead content of house dust. Refer to the Environmental Case Management of Lead Exposed Persons Guidelines for Public Health Units, Ministry of Health 2007 for further information.
8.4 Lead in soil
Children between the ages of one and five years are the group most likely to be exposed to lead in soil. At a conservative estimate, children may ingest up to 100 mg/day of soil. Thus, a stricter standard is required for soil in which children may play than for other soil. Investigation levels are those at or above which a risk assessment and contaminant source investigation should be initiated. Action levels are those at or above which there is potential for harm, and remedial action is necessary.
Table 6: Lead in soil
| Criteria | Lead level |
|---|---|
| Background level (bare soil) | <200 mg/kg (ppm) |
| Investigation level (bare soil) | 300 mg/kg (ppm) |
| Action level (bare soil) | 1000 mg/kg (ppm) |
| Action level (children's play area) | 300 mg/kg (ppm) |
Source: Environmental Case Management of Lead Exposed Persons Guidelines for Public Health Units, Ministry of Health 2007.