Occupational Silica Exposure and Chronic Kidney Disease

Figures & data

Table 1. Characteristics of patients with chronic kidney disease and community controls in North Carolina.

	CKD cases (N = 504)	Controls (N = 457)	p-Value
Mean age, years (SD)	62.8 (12.0)	61.6 (12.1)	0.11
White race	275 (54.6)	244 (53.4)	0.72
Male gender	298 (59.1)	271 (59.3)	0.96
Education level (years)
<8	193 (38.8)	120 (26.4)	<0.0001
8–11	150 (30.2)	134 (29.5)
12^a	154 (31.0)	200 (44.1)
Alcoholic drinks/day
<1	381 (75.6)	343 (75.15)	0.44
1–2	71 (14.1)	75 (16.4)
3^a	52 (10.3)	39 (8.5)
Moonshine consumption	57 (12.1)	36 (8.0)	0.04
Ever smoked	274 (55.0)	275 (61.3)	0.05
Mean PYs smoked, years (SD)	20.1 (29.6)	19.2 (27.9)	0.65
Mean BMI, kg/m^2 (SD)	26.9 (5.6)	25.4 (4.4)	<0.0001
History of diabetes	142 (28.8)	28 (6.1)	<0.0001
History of hypertension	305 (61.2)	135 (29.5)	<0.001
History of analgesic use
Never/occasionally	247 (54.2)	304 (70.2)	<0.0001
Weekly	129 (28.4)	106 (24.5)
Daily	79 (17.4)	23 (5.3)
Proxy respondents	273 (54.2)	41 (9.0)	<0.0001
CKD case subtypes
Nephrosclerosis	98 (19.4)	–
Diabetic nephropathy	95 (18.9)	–
Glomerular nephritis	68 (13.5)	–
Interstitial nephritis	100 (19.8)	–
End-stage renal disease (ESRD)^a	34 (6.8)	–
Renal insufficiency^a	109 (21.6)	–

Notes: CKD, chronic kidney disease; SD, standard deviation; PY, pack years; BMI, body mass index. N (%) unless noted differently.

^aNot otherwise specified.

Table 2. Occupational silica exposure among patients with chronic kidney disease and community controls in North Carolina.

	CKD cases (N = 504)	Controls (N = 457)
Any silica exposure^a, N (%)	246 (48.8)	184 (40.3)
Level of silica exposure, N (%)
None (not exposed)	177 (35.1)	194 (42.5)
Low (maybe exposed)	81 (16.1)	79 (17.3)
Medium (low/possible)	199 (39.5)	149 (32.6)
High (high/probable)	47 (9.33)	35 (7.7)
Median duration of silica exposure (years)
Weighted for certainty and intensity	22.5	13.0
Weighted for intensity only	30.0	18.0

Notes: CKD, chronic kidney disease.

^aDefined as medium or high level of silica exposure.

Table 3. Adjusted^a conditional odds ratios and 95% confidence intervals for chronic kidney disease subtypes associated with occupational silica exposure.^b

	OR (95% CI)
CKD (all)	1.37 (1.02, 1.85)
Nephrosclerosis	1.21 (0.72, 2.04)
Diabetic nephropathy	1.40 (0.82, 2.39)
Glomerulonephritis	1.13 (0.63, 2.03)
Interstitial nephritis	1.30 (0.76, 2.23)
ESRD	1.74 (0.76, 4.01)
Renal insufficiency	1.74 (1.05, 2.87)

Notes: CKD, chronic kidney disease; OR, odds ratio; CI, confidence interval.

^aAdjusted for age and education.

^bDefined as medium or high level of silica exposure versus not exposed or low silica exposure.

Figure 1. Age- and education-adjusted conditional odds ratios (and 95% confidence intervals) for chronic kidney disease associated with increasing duration of occupational silica exposure. Weighted for certainty and intensity; 370 cases and 329 controls with nonmissing silica duration data. Note: *Median silica duration = 13.0 years.

Table

Occupation	Industry	Industrial hygiene review: silica exposure rating based on prior knowledge of jobs and tasks		Self-report, on this job, exposed to
		Intensity	Certainty	Sand or silica	Dusty conditions
804: Truck drivers, heavy	060: Construction	High	High	Yes	Yes
613–617: Extractive occupation	040–050: Mining	High	High	No	Yes
563: Brick masons and stonemasons	060: Construction	High	High	Yes	Yes
869: Construction laborers	060: Construction	High	Moderate	Yes	Yes
453: Janitors and cleaners	130: Tobacco manufacturing	Moderate	High	No	Yes
585: Plumbers, pipefitters, and steamfitters	060: Construction	Moderate	Low	No	Yes
567: Carpenters	060: Construction	Low	Moderate	No	Yes
479: Farm workers	010–031: Agriculture, etc.	Low	Moderate	No	Yes
453: Janitors and cleaners	132–152: Textile manufacturing	Low	Low	No	Yes