Page 114 - Environmental Control in Petroleum Engineering

The Impact of Drilling and Production Operations 101

metals affect the action of enzymes. Excess concentrations of metals
inhibit normal biochemical processes in cells. This inhibition can result
in damage to the liver, kidney, or reproductive, blood forming,
or nervous systems. These effects may also include mutations or
tumors. Many metals can impact embryo and larval states of fish and
benthic invertebrates.
The toxicities of many metals found in the upstream petroleum
industry have been summarized by the American Conference of Govern-
mental Industrial Hygienists (ACGIH) and are listed in Table 3-8
(Proctor et al., 1989). This table lists the threshold limit values (TLV)
for airborne exposures.
The toxicity of trace metals in agricultural soils is summarized by
Logan and Traina (1993) and is given in Table 3-9. This table identifies
whether the element is essential, beneficial, or toxic to plants and
animals. Also found is a typical concentration of each metal in soils,
From this table it can be seen that many metals are essential in low
concentrations, but toxic in high concentrations.
A description of the health impacts of a number of heavy metals is
given below. Further information about these and other metals is
available in the literature, for example, Valkovic (1978), Proctor et al.

Table 3-8
Concentration Limits for Heavy Metals

Metal TLV (mg/m 3)
Aluminum 2.0
Arsenic 0.2
Barium (soluble compounds) 0.5
Barium (barium sulfate) 10
Cadmium 0.05
Chromium (trivalent) 0.5
Chromium (hexavalent) 0.05
Lead 0.15
Mercury 0.05
Nickel (soluble inorganic compounds) 0.1
Vanadium (as vanadium pentoxide) 0.05
Zinc (as zinc oxide) 5

Source: Proctor et al., 1989.
Copyright Van Nostrand Reinhold, with permission.