Case-control study of environmental toxins and risk of amyotrophic lateral sclerosis involving the national ALS registry

Figures & data

Table 1. Demographic characteristics at survey of 243 ALS cases and controls.

Characteristic	Cases (n = 243), n (%)	Controls (n = 243), n (%)
Sex
Male	150 (61.7)	150 (61.7)
Female	93 (38.3)	93 (38.3)
Race
White (or part White)	240 (98.8)	240 (98.8)
Black	3 (1.2)	3 (1.2)
Birth year
<1940	14 (5.8)	13 (5.4)
1940–1949	80 (32.9)	82 (33.7)
1950–1959	96 (39.5)	95 (39.1)
1960–1969	44 (18.1)	42 (17.3)
≥1970	9 (3.7)	11 (4.5)
Age at blood draw, years
Mean (SD)	62.9 (10.1)	67.4 (9.0)
Median (range)	64.1 (36-88)	68.4 (42-93)
Education^a
High school diploma/GED, technical trade	42 (17.3)	39 (16.0)
Some college	36 (14.8)	35 (14.4)
College graduate	83 (34.2)	96 (39.5)
Postgraduate	79 (32.5)	73 (30.0)
U.S. Census Region
Northeast	40 (16.5)	40 (16.5)
Midwest	69 (28.4)	69 (28.4)
South	71 (29.2)	71 (29.2)
West	63 (25.9)	63 (25.9)
Ever member of armed forces
Yes	53 (21.8)	55 (22.6)
No	190 (78.2)	188 (77.4)
Deployment
Yes	16 (6.6)	15 (6.2)
No	227 (93.4)	228 (93.8)
Smoking status
Never smoker	138 (56.8)	160 (65.8)
Ever smoker (≥1 cigarette/day for 6+ months)	105 (43.2)	83 (34.2)

^aEducational level is unknown for three cases.

Table 2. Distribution of observed organochlorine pesticides detection levels and analytical strategies among 243 cases and controls.

Pesticide	Cases (N = 243) (ng/g)				Controls (N = 243) (ng/g)
	N (%)	10^th	50^th	90^th	N (%)	10^th	50^th	90^th
4,4′-DDE	243 (100)	36.4	96.9	387.0	243 (100)	41.4	105.0	338.0
Hexachlorobenzene	243 (100)	5.5	7.8	13.1	243 (100)	5.3	7.8	11.5
trans-Nonachlor	241 (99.2)	6.5	16.1	40.5	237 (97.5)	7.7	16.2	41.4
β-Endosulfan	234 (96.3)	24.4	34.6	48.9	221 (90.9)	14.9	36.5	62.3
α-Endosulfan	226 (93.0)	13.2	19.5	28.3	188 (77.4)	9.0	18.1	33.6
oxy-Chlordane	170 (70.0)	5.5	12.2	29.9	203 (83.5)	5.2	10.7	25.2
cis-Nonachlor	121 (50.0)	4.0	6.5	11.6	127 (52.2)	3.0	5.6	8.4
Mirex	68 (28.0)	3.4	5.0	15.4	78 (32.1)	2.5	5.0	15.6
β-HCH	66 (27.2)	4.4	7.8	24.2	67 (27.6)	2.4	6.3	15.3
cis-Chlordane	51 (21.0)	3.6	5.3	11.9	52 (21.4)	2.3	4.5	12.1
trans-Chlordane	33 (13.6)	3.2	4.2	7.7	21 (8.6)	2.2	4.3	6.6
Dieldrin	27 (11.1)	7.5	11.3	23.1	43 (17.7)	4.4	11.4	25.8
Heptachlor	24 (9.9)	3.0	4.6	7.1	7 (2.9)	1.6	4.0	6.5
Heptachlor Epoxide	21 (8.6)	8.8	13.4	23.1	26 (10.7)	3.9	11.7	42.4
4,4′-DDT	12 (4.9)	5.8	11.9	26.9	7 (2.9)	2.2	4.2	395.0
Low detection in the population^a
γ-HCH	11 (4.5)	–	–	–	2 (0.8)	–	–	–
Endrin Aldehyde	8 (3.3)	–	–	–	4 (1.6)	–	–	–
2,4′-DDT	4 (1.6)	–	–	–	1 (0.4)	–	–	–
α-HCH	4 (1.6)	–	–	–	5 (2.1)	–	–	–
Aldrin	2 (0.8)	–	–	–	6 (2.5)	–	–	–
Endosulfan Sulfate	1 (0.4)	–	–	–	5 (2.1)	–	–	–
δ-HCH	1 (0.4)	–	–	–	0 (0)	–	–	–
2,4′-DDD	0 (0)	–	–	–	2 (0.8)	–	–	–
2,4′-DDE	0 (0)	–	–	–	2 (0.8)	–	–	–
4,4′-DDD	0 (0)	–	–	–	2 (0.8)	–	–	–
Endrin	0 (0)	–	–	–	1 (0.4)	–	–	–
Endrin Ketone	0 (0)	–	–	–	0 (0)	–	–	–
Methoxychlor	0 (0)	–	–	–	0 (0)	–	–	–
Toxaphene	0 (0)	–	–	–	0 (0)	–	–	–

^a Low detection of OCP levels is defined as OCPs with too few measurable samples (i.e. <5%).

Table 3. Spearman rank-order correlation matrix for cases and controls using self-reported total years of exposure to residential pesticides.

	4,4’-DDE	Hexachloro-benzene	trans-Nonachlor	β-Endosulfan	α-Endosulfan	Oxychlordane
Cases (Coefficient*, P value **, Number of observations***)
Insecticides in the home	*0.27	0.17	0.24	0.077	0.093	0.25
	**0.001	0.042	0.003	0.36	0.28	0.012
	***146	146	144	141	137	97
Insecticides in the yard	0.28	0.23	0.30	0.086	0.033	0.20
	0.001	0.008	<0.001	0.32	0.71	0.053
	137	137	136	133	126	93
Herbicides	0.21	0.18	0.20	0.009	0.032	0.20
	0.007	0.046	0.012	0.91	0.70	0.042
	162	162	161	157	151	107
Chemical pet soaps	0.11	0.077	0.24	0.20	−0.044	0.26
	0.25	0.43	0.014	0.042	0.67	0.030
	106	106	104	101	99	70
Controls (Coefficient*, P value **, Number of observations***)
Insecticides in the home	*0.13	0.087	0.24	0.019	0.048	0.25
	**0.094	0.25	0.001	0.81	0.57	0.002
	***180	180	178	169	145	156
Insecticides in the yard	0.13	0.089	0.25	0.076	0.072	0.18
	0.13	0.31	0.003	0.41	0.46	0.054
	132	132	132	118	108	113
Herbicides	0.23	−0.007	0.24	0.11	0.095	0.19
	0.002	0.93	0.002	0.19	0.28	0.027
	167	167	164	148	133	138
Chemical pet soaps	0.22	0.12	0.21	0.056	0.002	0.27
	0.027	0.24	0.030	0.59	0.99	0.010
	105	105	104	99	81	90

Figure 1. Odds ratios for the Risk of ALS and OCPs.

Table 4. Occupational, residential, and avocational exposures to pesticides, solvents, and lead in 243 ALS cases and matched controls^a.

	Self-Reported Exposure		Duration of Exposure^b
Survey: Self-reported Exposure	Case/control pairs	OR (95% CI)	OR (95% CI)
Occupational Exposure
Ever Pesticides on job^c	226	0.80 (0.42, 1.50)	–
Ever Solvent on job^d	228	1.27 (0.82, 1.97)	–
Ever Lead on job^e	232	1.77 (1.11, 2.83)	–
Residential Exposure^f
Insecticides in home	230	0.56 (0.37, 0.84)	0.99 (0.98, 1.00)
Insecticides in lawn	229	1.32 (0.91, 1.91)	1.01 (1.00, 1.02)^g
Herbicides in lawn or garden	231	1.03 (0.68, 1.56)	1.01 (1.00, 1.02)
Fungicides in home or garden	230	1.09 (0.65, 1.82)	1.02 (0.99, 1.04)
Applied chemical soaps, shampoos, dips, or powders on a pet	233	1.03 (0.71, 1.50)	1.01 (1.00, 1.03)
Hobby Exposure
Ever Solvent with hobby^h	207	1.29 (0.80, 2.07)	–
Ever Lead with hobby^i	204	1.53 (0.94, 2.50)	–
Ever Gardening exposure ^j	210	1.57 (1.04, 2.37)	–
Residential Characteristics^k
Live on a farm or ranch	218	0.83 (0.51, 1.34)	1.00 (0.99, 1.02)
Live within 1/4 mile of agricultural area that sprayed with pesticides or herbicides	157	0.82 (0.50, 1.35)	1.00 (0.98, 1.01)
Main source of drinking water a private well	195	0.72 (0.46, 1.14)	0.99 (0.98, 1.00)

^a Adjusted for smoking and education.

^b Duration of Exposure = the age of last use to the age of first use minus the years of no use. No ORs (Odds Ratios) available for occupational or hobby exposure as ever/never categories precluded assessment of duration and risk.

^c Any job where handled herbicide, fungicide, insecticide, rodenticides, or fumigants for at least 100 days or more during your lifetime.

^d Any job where handled glue or adhesives, solvents and degreasers, unleaded gasoline, unleaded paint, and formaldehyde for at least 100 days or more during your lifetime.

^e Any job where soldered, welded, brazed or flame cut metals, exposed to metal dust or fumes, or handled leaded paint or leaded gasoline for at least 100 days or more during your lifetime.

^f Residential exposure: Ever personally handled pesticides from age 10 years old to the present.

^g Borderline significant.

^h Solvent hobby: Ever woodworked, repaired or restored old cars, built models using glue, or developed photographs from age 10 years old to the present on a regular basis, for at least one hour each month for at least one year or more.

ⁱ Lead hobby: Ever made lead glazed pottery, used oil-based paint, or did home remodeling projects, metal work, hunting, gun shooting at a range, casing bullets or reload ammunition, or fishing with lead weights from age 10 years old to the present on a regular basis for at least one hour each month for at least one year or more.

^j Gardening hobby: Ever gardened from age 10 years old to the present on a regular basis, for at least one hour each month for at least one year or more.

^k Residences lived in for 6 months or more.