The cause-specific lagged relative risks (RR) of mortality across the life course (from birth to 100 years) for an older diplomat in the Standard A assignment are included in Fig. 2. There were no lags applied prior to the beginning of the diplomatic assignment and an inception lag was applied during years 1–4, 11–14, and 18–19 of the Standard A assignment when the diplomat lived in a city with ambient annual PM2.5 that was at least 5 µg/m3 greater than the prior city location and a cessation lag was applied during years 5–10, 15–17, and 20 when the diplomat moved to a city with ambient annual PM2.5 at least 5 µg/m3 less than the prior city’s PM2.5 annual mean. A cessation lag was also applied at the conclusion of the diplomatic assignment from age 65–84 years.
After the older diplomat began the Standard A assignment at age 45, among the six pollution-sensitive conditions, the greatest difference between RRs for the diplomat compared to the RR for the person who lived exclusively in the US was observed for stroke (Fig. 2B) during the fifteenth year of the assignment, during the third and final year working in Bangkok, Thailand with an RR of 1.39 (95% CI: 1.23, 1.57) and mean annual PM2.5 of 27 µg/m3. During the same year, the RR of stroke for a person living in the US was 1.07 (1.0, 1.17) and mean annual PM2.5 of 9 µg/m3. During the course of the 20-year Standard A assignment, the RRs of mortality for each of the six pollution sensitive conditions have three distinct peaks, each occurring at the conclusion of a series of years with consecutively increasing ambient PM2.5 levels. The pollution sensitive condition with the second greatest annual difference in the RR of mortality during the Standard A assignment for a diplomat compared to a person living in the US was for IHD, with an RR of 1.29 (95% CI: 1.14, 1.49), during the third an final year working in Bangkok when the mean annual PM2.5 was 27 µg/m3 (Fig. 2A). During the same year, the RR of IHD for a person living in the US was 1.04 (95% CI: 1.00, 1.15) and mean annual PM2.5 of 9 µg/m3, and the confidence intervals (CIs) for the diplomat and the person of comparable age living in the US overlap. The RRs of mortality for IHD and stroke are elevated before the older diplomat began the Standard A assignment at age 45 and these RRs are reflective of the GBD C-R functions based on US PM2.5 levels. Supplementary Fig. 3 shows the pollution sensitive condition iMRs for an older diplomat in the Standard A assignment.
Figure 3 shows the deaths per one million persons due to all-causes, that incorporates the individual pollution sensitive iMRs for female older diplomats in various assignments. The assignment “High 3 years & low 1 year cycle” has the highest impacted mortality rate each year compared to the other assignments for most of the 20-year assignment period, from ages 45–64, although the CIs for the three assignments overlap in 19 of the 20 years of diplomatic postings. The CIs for the “High 3 years & low 1 year cycle” and the “High 2 years & low 2 years cycle” assignments do not overlap with the CIs for the US iMRs. However, the CIs for the assignment with the least number of years in a location with high PM2.5, “High 1 year & low 3 years cycle”, overlap with the CIs for the US iMRs during 19 of the 20 years of the diplomatic assignments. Beginning at age 65 after the completion of the assignments, the iMRs for the three assignments gradually decline to the US MR.
During the Standard A and Standard B assignments, older diplomats had a greater number of excess deaths due to international assignments than young diplomats and children accompanying a parent on diplomatic assignments (Table 1). During the Standard A assignment, older diplomats (12,246.8 deaths per one million males, 6,640.7 deaths per one million females) had 8 times as many excess deaths as young diplomats (1,527.9 deaths per one million males, 708.6 deaths per one million females) and more than a 600-fold increase in excess deaths compared to a child accompanying their parent(s) on a diplomatic assignment (20.1 deaths per one million males, 12.1 deaths per one million females). Among the assignments examined, older diplomats living in one city with very high PM2.5 for 20 years had the highest number of excess deaths due to international assignments (49,140.4 deaths per one million males, 28,758.3 deaths per one million females), followed by living in a series of high PM2.5 cities in the assignment “High 4 years x 5” (29,658.2 deaths per one million males, 16,517.3 deaths per one million females). Among older diplomats in assignments with one, two or three of every four years living in locations with high PM2.5 (PM2.5 annual mean between 41 to 60 µg/m3), the highest number of excess deaths were found during assignments with the highest number of years in cities with high PM2.5 locations, including the assignments “High 3 years & low 1 year cycle” (22,120.1 deaths per one million males, 12,329.7 deaths per one million females), “High 2 years & low 2 years cycle” (15,496.9 deaths per one million males, 8,555.1 deaths per one million females) and “High 1 year & 3 low years cycle” (10,009.2 deaths per one million males, 5,409.8 deaths per one million females).
Table 1
Number of excess deaths1per one million persons for each diplomatic assignment2
|
|
Older diplomat
|
|
Young diplomat
|
|
Child
|
Assignment
|
Assignment description3
|
Excess deaths, male
|
Excess deaths, female
|
|
Excess deaths, male
|
Excess deaths, female
|
|
Excess deaths, male
|
Excess deaths, female
|
1
|
Standard A
|
12,246.8
|
6,640.7
|
|
1,527.9
|
708.6
|
|
20.1
|
12.1
|
2
|
Standard B
|
10,568.4
|
5,623.3
|
|
1,341.8
|
562.7
|
|
43.7
|
27.9
|
3
|
Standard A x 2
|
n/a
|
n/a
|
|
14,370.6
|
7,896.7
|
|
n/a
|
n/a
|
4
|
High 1 year & low 3 years cycle
|
10,009.2
|
5,409.8
|
|
1,171.2
|
536.3
|
|
40.7
|
26.7
|
5
|
High 2 years & low 2 years cycle
|
15,496.9
|
8,555.1
|
|
2,050.4
|
975.8
|
|
60.3
|
37.9
|
6
|
High 3 years & low 1 year cycle
|
22,120.1
|
12,329.7
|
|
3,007.8
|
1,466.6
|
|
75.7
|
44.4
|
7
|
High 4 years x 5
|
29,658.2
|
16,517.3
|
|
7,695.6
|
5,211.2
|
|
86.8
|
53.1
|
8
|
Very high 2 years & low 2 years cycle
|
24,988.7
|
14,514.8
|
|
3,304.8
|
1,678.9
|
|
108.5
|
70.7
|
9
|
Very high 20 years
|
49,140.4
|
28,758.3
|
|
6,332.1
|
3,321.5
|
|
163.5
|
103.8
|
10
|
Standard A with mitigation4
|
4,119.6
|
2,117.3
|
|
406.0
|
148.8
|
|
-1.8
|
-0.9
|
1The number of excess deaths per year i is calculated by subtracting the number of deaths during year i per 1 million persons of the same age and sex living exclusively in the US from the number of deaths during year i per 1 million diplomats completing a diplomatic assignment. The number of excess deaths listed on this table is the sum of excess deaths for each year from birth to age 100.
2See Supplemental Table 1 for a list of cities and number of years in each city during the 10 assignments and see Fig. 1 for the annual mean PM2.5 levels used in the calculations.
3Ambient PM2.5 level descriptions include low (PM2.5<20 µg/m3), moderate (PM2.5 21–40 µg/m3), high (PM2.5 41–60 µg/m3) and very high
(PM2.5>61 µg/m3)
4 In this assignment, diplomats used air purifiers in their residences while working in cities in Africa and Asia.
Older diplomats had greater DLL than young diplomats in the Standard A assignment (80.4 DLL vs. 10.4 DLL) and in the Standard B assignment (84.1 DLL vs. 25.0 DLL) (Fig. 4). Similar trends were found for females, although the magnitude of impact was smaller than that of males. Among older male diplomats, the greatest DLL were observed during the assignment in one city with very high PM2.5 for 20 years, “Very high 20 years” (287.8 DLL), followed by serving in four cities with high PM2.5 for a total of 20 years, “High 4 years x 5” (176.9 DLL), and an equal number of years in cities with very high PM2.5 and low PM2.5, “Very high 2 years & low 2 years” (152.8 DLL). Among older male diplomats completing assignments with one, two or three of every four years in a city with high PM2.5, the “High 3 years & 1 low year cycle” (132.9 DLL) assignment had the highest number of DLL among older male diplomats. The magnitude of DLL decreased as the number of years in cities with high PM2.5 per four year cycle decreased to a low of 72.4 DLL while serving in the assignment with one year in a city with high PM2.5,“High 1 year & low 3 years cycle”. A male completing a 40-year assignment, “Standard A x 2” from ages 25–64 years (89.7 DLL) had only slightly higher DLL than a male completing the Standard A assignment for 20 years from ages 45–64 (80.4 DLL).
Figure 4: Days of life lost associated with assignments for diplomats in three age groups
The RRs of cause-specific mortality for an older diplomat in the Standard A assignment with mitigation (Fig. 5) were much closer to that of a person of the same age and sex living in the US than in the Standard A assignment without mitigation. Similarly, the number of deaths per million older female diplomats in the Standard A assignment with mitigation (Fig. 6) were much closer to that of a person of the same age and sex living in the US than in the Standard A assignment without mitigation. Examining the number of excess deaths among male diplomats for the Standard A assignment with mitigation compared to the Standard A assignment without mitigation, excess deaths decreased by 66% for older diplomats (from 12,246.8 to 4,119.7 deaths per million), 73% for young diplomats (from 1,527.9 to 406.0 deaths per million) and 49% for children of diplomats (from 3.5 to 1.8 deaths per million) (Table 1). Among males the DLL decreased by 60% for older diplomats (from 80.4 to 32.0 DLL), 55% for young diplomats (from 10.4 to 4.7 DLL) and results were similar in both scenarios for children (0.4 and − 0.1 DLL).
Figure 6: Deaths per million female older diplomats in the Standard A assignment without mitigation
The differences in DLL for the specified sensitivity analysis options were quantified by subtracting the DLL from the main model reported above: the differences in DLL ranged from − 48.0 to + 55.1 for older diplomats, − 9.7 to + 15.7 for young diplomats and − 1.2 to + 2.4 for children (Fig. 7). Removing the inception lag had the largest impact on the DLL among the investigated model variations for older diplomats (+ 55.2 (+ 68%) DLL male, + 36.4 (+ 76%) DLL female) and younger diplomats (+ 15.7 (+ 151%) DLL male, + 9.4 (+ 90%) DLL female). Using the upper CI of the C-R function also resulted in an increase in DLL both among older diplomats (+ 22.5 (+ 28%) DLL male, + 15.6 (+ 33%) DLL female) and young diplomats (+ 12.0 (+ 115%) DLL male, + 7.3 (+ 70%) DLL female). Using the short lag on COPD and LRI and, separately, the long lag on lung cancer, both had small impacts on the DLL for older and young diplomats. Model variations applied to older diplomats resulted in a decrease in DLL: removing lags from the model (-16.3 (-20%) DLL male, -13.9 (-29%) DLL female), using the minimum C-R function (-17.1 (-21%) DLL male, -14.2 (-30%) DLL female), using high income mortality rates (-28.2 (-35%) DLL male and female) and removing the cessation lag (-48.0 (-59%) DLL male, -34.0 (-71%) DLL female). Application of the short lag to COPD and LRI suggested the largest possible impacts on DLL for children (+ 2.9 (+ 431%) DLL male, female + 1.8 (+ 465%) DLL female). All other model variations resulted in less than 1 DLL gained or lost. Use of high income US baseline mortality statistics, instead of mortality statistics for the entire US population, resulted in a slight gain in DLL (+ 0.7 (+ 103%) DLL male, (+ 0.4 (+ 95%) DLL female) as did removal of the cessation lag for all six pollution sensitive conditions (+ 0.7 (+ 100%) DLL male, + 0.5 (+ 100%) DLL female). Use of the 20-year inception and cessation lags yielded results that were roughly midway between the results when other elements of the model were changed.
Figure 7: Change in the DLL in sensitivity analysis for diplomats in three age groups