Abstract:
Coal tars have been identified as posing a threat to human health due to their
toxic, mutagenic and carcinogenic characteristics. Workers involved in former
gasholders decommissioning are potentially exposed to relevant concentrations of
volatile and semi-volatile hydrocarbons upon opening up derelict tanks and
during tar excavation/removal. While information on contaminated sites air-
quality and its implications on medium-long term exposure is available, acute
exposure issues associated with the execution of critical tasks are less
understood. Calculations indicated that the concentration of a given contaminant
in the gasholder vapour phase only depends on the coal tar composition, being
only barely affected by the presence of water in the gasholder and the tar
volume/void space ratio. Fugacity modelling suggested that risk-critical
compounds such as benzene, naphthalene and other monocyclic and polycyclic
aromatic hydrocarbons may gather in the gasholder air phase at significant
concentrations. Gasholder emissions were measured on-site and compared with the
workplace exposure limits (WELs) currently in use in UK. While levels for most
of the toxic compounds were far lower than WELs, benzene air-concentrations
where found to be above the accepted threshold. In addition due to the long
exposure periods involved in gasholder decommissioning and the significant
contribution given by naphthalene to the total coal tar vapour concentration,
the adoption of a WEL for naphthalene may need to be considered to support
operators in preventing human health risk at the workplace. The Level I fugacity
approach used in this study demonstrated its suitability for applications to
sealed environments such as gasholders and its further refining could provide a
useful tool for land remediation risk assessors. (C) 2008 Elsevier Ltd. All
rights reserved.
