Not all emissions from waste incinerators are monitored or measured in any way. A list of some of these is available from http://www.ukwin.org.uk/?page_id=78. Even monitored emissions are not always continuously checked, and this can result in underestimates.
Spot monitoring, unlike continuous monitoring, only measures pollutant emissions at occasional intervals. For example, spot monitoring in this context may involve monitoring emissions just twice per year (once every 6 months).
The duration of the sampling period for the measurements will typically be much shorter than the interval between monitoring activities. For example, the sampling period may last between 6 and 8 hours. So over a period of 6 months of emissions, the only data collected for those emissions would be during one monitoring activity at the start of the 6 month period and one at the end. For two sampling durations of 7 hours each that represents just 0.3 percent of the time between measurements (6 months). In other words, the emission rate is only known for 0.3 percent (14 hours) of 6 months, and is unknown for the remaining 99.7 percent of the time. Hence, spot monitoring may be unrepresentative of the actual emissions [Bostock, A., Waste Incineration and its Impact on Health, the Environment, and Sustainability (2005). Available from; purl.org/net/acrologicrecycled/incineration].
A Belgian study showed that spot measurements do not give a representative indication of the actual emissions over a period [De Fré, R. and Wevers, M. Organohalogen Compounds. 36, 17-20 (1998)]. Continuous monitoring over a period showed that actual emissions could be 30 to 50 times higher than those recorded by spot measurements.
The spot monitoring of emissions of dioxins and furans (and heavy metals) represents a potential cause for concern because:
1. Spot monitoring may not represent actual emissions during the (6 or 12 month) period between measurements. Therefore, the actual impact on health and the environment may be worse than predicted.
2. If excessive emissions did occur between measurements then the operator, the regulator and the public would be unaware of the incident. This means that steps could never be taken to stop such incidents developing, because they would not be detected. It also means that the public could not be warned at the time of the incident to take precautionary measures. A worst case scenario might mean that the public and the environment become significantly contaminated, but the effects do not become apparent until many years later (e.g. in the form of cancers). Again, the inability to detect the incident, at the time, means that potential cleanup operations (e.g. of the environment, soil on agricultural land, gardens, allotments and contaminated food) would not take place until years after the damage had been done.
And more on health impacts of nanoparticles can be found at