The effect of refurbishing a UK steel plant on PM10 metal composition and ability to induce inflammation

Abstract

Background: In the year 2000 Corus closed its steel plant operations in Redcar, NE of England temporarily for refurbishment of its blast furnace. This study investigates the impact of the closure on the chemical composition and biological activity of PM10 collected in the vicinity of the steel plant.

Methods: The metal content of PM10 samples collected before during and after the closure was measured by ICP-MS in order to ascertain whether there was any significant alteration in PM10 composition during the steel plant closure. Biological activity was assessed by instillation of 24 hr PM10 samples into male Wistar rats for 18 hr (n = 6). Inflammation was identified by the cellular and biochemical profile of the bronchoalveolar lavage fluid. Metal chelation of PM10 samples was conducted using Chelex beads prior to treatment of macrophage cell line, J774, in vitro and assessment of pro-inflammatory cytokine expression.

Results: The total metal content of PM10 collected before and during the closure period were similar, but on reopening of the steel plant there was a significant 3-fold increase (p < 0.05) compared with the closure and pre-closure samples. Wind direction prior to the closure was predominantly from the north, compared to south westerly during the closure and re-opened periods. Of metals analysed, iron was most abundant in the total and acid extract, while zinc was the most prevalent metal in the water-soluble fraction. Elevated markers of inflammation included a significant increase (p < 0.01) in neutrophil cell numbers in the bronchoalveolar lavage of rats instilled with PM10 collected during the reopened period, as well as significant increases in albumin (p < 0.05). Extracts of PM10 from the pre-closure and closure periods did not induce any significant alterations in inflammation or lung damage. The soluble and insoluble extractable PM10 components washed from the reopened period both induced a significant increase in neutrophil cell number (p < 0.05) when compared to the control, and these increases when added together approximately equalled the inflammation induced by the whole sample. PM10 from the re-opened period stimulated J774 macrophages to generate TNF-alpha protein and this was significantly prevented by chelating the metal content of the PM10 prior to addition to the cells.

Conclusion: PM10-induced inflammation in the rat lung was related to the concentration of metals in the PM10 samples tested, and activity was found in both the soluble and insoluble fractions of the particulate pollutant.

Figure 1

Map of Redcar and surrounding industrial sites. AUN TEOM collection site in proximity to the blast furnace.

Figure 2

Diagram detailing the methods used to prepare samples to examine composition and toxicity of Redcar PM₁₀.

Figure 3

Wind rose illustrating speed (knots) and direction of the wind every 15 minutes y-axis represents the number of 15 minute occurrences with the x-axis's representing direction in degrees. (a) Sampling before the closure of the blast furnace (1/6/00 – 25/6/00). (b) During the closure of the blast furnace (26/7/00 – 28/9/00). (c) Sampling after the blast furnace reopened (29/9/00–31/12/00) and (d) the total sampling period (1/6/00–31/12/00).

Figure 4

The measured metal content of 7 day PM₁₀ samples collected before, during and after closure (* p < 0.05 compared to closure period). Extracts were made into ultra pure water (aqueous extract) followed by digestion of the remaining filter in HCl:HNO₃(acid extract). Measurements were conducted by ICP-MS and values are the mean of 2 samples ± SEM.

Figure 5

Metal content of PM₁₀ collected before, during and after the closure of the Redcar Corus steel plant. (a) Aqueous extractable (b) acid extractable metal content of PM₁₀. Measurements were conducted by ICP-MS and values are of individual filter samples

Figure 6

The mean neutrophil number in bronchoalveolar lavage from rat's 18 hr after exposure to either (a) total aqueous extracts or (b) the soluble or insoluble fractions of aqueous extracts of PM₁₀ samples collected before, during and after the steel plant closure. Control animals were instilled with saline. Values represent the mean of (a) 6 and (b) 3 rats ± SEM (** p < 0.01 and * p < 0.05 to control, $ p < 0.05 closed to reopened

Figure 7

The mean concentration of albumin protein in BAL fluid from lungs exposed to aqueous extracts of PM₁₀ and saline control (* p < 0.05 to control). Values represent the mean of 3 experiments ± SEM.

Figure 8

The mRNA expression by rat bronchoalveolar lavage cells 18 hr following instillation of aqueous extracts of PM₁₀ collected before, during and after the steel plant closure (* p < 0.05 to control). Values represent the mean of 6 rats ± SEM.

Figure 9

TNFα protein production in J774.A1 cells treated for 4 hrs with Redcar PM₁₀sample during and after the closure of the Corus plant and identical samples which underwent 4 hrs of chelating treatment. *p < 0.05 when compared to control, $p < 0.05 when compared to untreated reopened PM₁₀ samples. Values represent the mean of 3 experiments ± SEM.